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"Assessment and Recommendations for a Consolidated European Approach to Space Weather – as Part of a Global Space Weather Effort"

European Space Weather Assessment and Consolidation Committee – ESWACCReport (Full Version – August 30, 2019)

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Hermann J. Opgenoorth, Robert F. Wimmer-Schweingruber, Anna Belehaki, David Berghmans, Mike Hapgood, Michal Hesse, Kirsti Kauristie, Mark Lester, Jean Lilensten,

Mauro Messerotti, and Manuela Temmer

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Opgenoorth HJ, Wimmer-Schweingruber RF, Belehaki A, Berghmans D, Hapgood M, et al. 2019. Assessment and recommendations for a consolidated European approach to space weather – as part of a global space weather effort. J. Space Weather Space Clim., 9 (2019) A37. https://doi.org/10.1051/swsc/2019033

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EuropeanSpaceWeatherActivitiesAssessmentandRecommendationsforaConsolidatedEuropeanApproach to SpaceWeather – asPartof aGlobalSpaceWeatherEffort

EuropeanSpaceWeatherAssessmentandConsolidationCommittee–ESWACC

Report(FullVersion–August30,2019)

Committeemembers:Chair: HermannJ.Opgenoorth ESSCSolarSystemExplorationPanelChair UniversityofUmeå,Sweden andUniversityofLeicester,UKCo-Chair: RobertWimmer-Schweingruber ESSC Solar System Exploration Panel

Member UniversityofKiel,GermanyExpertMembers:AnnaBelehaki,NOA,Athens,Greece DavidBerghmans,ROB,Brussels,BelgiumMikeHapgood,RAL,UK MichalHesse,UoBergen,NorwayKirstiKauristie,FMI,Helsinki,Finland MarkLester,UoLeicester,UKJeanLilensten,UoGrenoble,France MauroMesserotti,INAFandUoTrieste,ItalyManuelaTemmer,UoGraz,AustriaEx-officioJuha-PekkaLuntama,ESA-SSA,MatsLjungqvist,EC-DGGrowth,andGeorgPeter,EC/JointresearchCentre(NOTE: the ex-officio representatives are not co-authoring this report, but have givenvaluablecommentsandadvicethroughouttheprocessofmeetingsanddiscussions)

AreportcommissionedbytheEuropeanSpaceScienceCommitteeESSC,oftheEuropeanScienceFoundationESFinMay2017.

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ProcessStartingwithafirstmeetingatESOCinDarmstadtinJune2017,ESWACChasheldfourface-to-facemeetings,atROBinBrussels,atESA-ESTECinNoordwijk,andattheUNinVienna.ThisreportwascompletedfollowinganumberofteleconferencesalsotoprepareslideswithpreliminaryfindingsandrecommendationasrequestedbytheEU/DG-GrowthinFebruary2018andanothersetofslideswiththefinalESWACCfindingsandrecommendationsfortheDGofESA,Dr.JanWörneratESAHQinFebruary2019.Thenext-to-finalreportwaspresentedtotheESSCPlenaryMeetinginAmsterdamonMay9-10, and after further iteration and helpful comments from Profs. Dan Baker, LASP,Boulder,USA, IanMann,U.ofAlberta,Canada,TimFuller-Rowell,CIRES,U.ofColoradoandNOAA,USA,andKarelSchrijver,LockheedPaloAlto(retired),USA.

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ContentsExecutiveSummary.................................................................................................................5

Purposeofthisdocument........................................................................................................8

1. Introduction.....................................................................................................................9

1.1. Background-Spaceweatherasaglobalchallenge.......................................................11

1.2. Pastandon-goingEuropeanSWxactivitiesandtheirposition inthe internationalframework.................................................................................................................................13

1.3. OtherRemainingChallenges.........................................................................................17

2. FindingsandRecommendations.....................................................................................18

2.1. Area 1: Imminent Need for Critical Research with Dedication to Enable SpaceWeatherUnderstandingandPrediction...................................................................................19

2.2. Area 2: Support to system-science approach with Coupled Physics-basedModelling:Sun/SolarWind/Magnetosphere/Ionosphere/Atmosphere............................31

2.3. Area3:ConsolidationofNational,RegionalandEuropeanRiskAssessments.............34

2.4. Area4:ConsolidationofEuropeanUserRequirements................................................39

2.5. Area 5: “R2O” and “O2R” or how can SWx scientists interface with candidateorganisationsforSWxservices–inEuropeandglobally..........................................................45

2.6. Area 6: Define and implement a network of space and ground-based assets forfutureSWxobservations...........................................................................................................47

3. Conclusions,OverarchingRecommendationsandFutureProspects................................51

4. References(inalphabeticalorder).................................................................................54

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ExecutiveSummaryOverthelast10-20yearstherehasbeenanever-increasinginternationalawarenessofrisksto modern society from adverse and potentially harmful – and in extreme cases evendisastrous – space weather events. Many individual countries and even internationalorganisations like the United Nations (UN) have begun to increase their activities inpreparing forandmitigatingeffectsofadverse spaceweather.As in the restof theworldthere is also in Europe an urgent need for coordination of Space Weather efforts inindividualcountriesaswellas inandamongEuropeanorganisationssuchastheEuropeanSpaceAgency(ESA)andtheEuropeanUnion(EU).Thiscoordinationshouldnotonlyimproveour ability tomeet spaceweather risks, but alsoenable Europe to contribute toon-goingglobal spaceweatherefforts.While spaceweather isaglobal threatwhichneedsaglobalresponse it also requires tailored regional and trans-regional responses that requirecoordinationatalllevels.Thisreportdiscusseson-goingEuropeanSWx(inthefollowingwewilladopttheUSstandardabbreviation“SWx”forSpaceWeather)effortsand issues,andgivesrecommendationsforfuturecoordinatedandbetterconsolidatedactivities.Wehavefoundthattheseissuescanbebrokendowninto6activitieswherecoordinationatEuropeanlevelwillberequired.Thisreportmakesrecommendationsinthesesixareas-asdefinedby:

1. Area1:EnablingcriticalsciencetoimproveourscientificunderstandingofSWx:Our overall description of the coupled Sun-Earth system in the space age stillcontainscriticalgapsinthescientificunderstandingofseveralmechanismsthroughwhich space weather couples from space all the way down to Earth. Whilesignificant progress can and will be made using existing scientific infrastructureincluding existing multi-spacecraft missions and ground-based networks, supportmust urgently be provided for the next generation space missions and thereplacementofageingground-basedinfrastructure.

2. Area 2: Development and coupling of advanced models by applying a system-scienceapproachwhichutilisesphysics-basedmodelling:Develop better physics-based models and also define metrics that facilitateassessmentofdifferentmodelsandtoencouragetheirtransitiontooperations.

3. Area3:AssessmentofrisksatNational,RegionalandEuropeanlevels:EuropeanStatesshouldregularlyassesstheirexposuretoSWxrisksandcoordinateand combine their studies at regional and European level to cover theinterdependency of technological infrastructures. This requires close cooperationbetweendecisionmakers,SWxscientists,serviceproviders,andend-users.

4. Area4:ConsolidationofEuropeanUserRequirementsEuropeanSWxuserrequirementsshouldbe(re-)assessedandprioritisedtakingintoaccountregionalandsocietaldifferencesandneeds,alsoaddressingdifferentneedsofvariousinfrastructuresystems.Thisshouldbedoneonaregularbasis,e.g.every5years,alsotofacilitatetheexchangeofinformationamongEuropeanSWxactors.

5. Area5:SupporttoR2O(andO2R)

The best available knowledge and models should be used in future SWx serviceorganisations. Such transition from Research to Operations should be guided by

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teams of scientists all over Europe - following the distributed ESA Expert ServiceCentre approach. In addition, a structure to enable models that have beentransitionedtooperationstobeimproved(O2R)shouldbeestablished.

6. Area6:DefineandimplementanoperationalnetworkforfutureSWxobservations

Basedonour present scientific understanding and the above assessments of risksanduserrequirementsweneedtodefineanoperationalspace-andground-basednetworkthatmeasuresessentialspaceweatherparameterswhichinturncandrivetheSWxpredictionsrequiredtoprotectoursociety’sinfrastructure.

OtherIssuesrequiringattention:A firstanalysisofourknowledge,observationalgapsand requirements foranappropriateSWx warning system with special consideration of European SWx vulnerabilities andweaknesses, but also taking into account European strengths has been carriedout by theExpertGroupsintheESASSASpaceWeatherServiceNetworkandtheresultsoftheanalysishavebeenreviewedbytheEuropeanSpaceWeatherWorkingTeam.However,continuouselaboration of the analysis including assessment of space weather risks on Europeaninfrastructure and understanding of the user needs will be required because of theconstantlyevolvingenduserlandscapeandEuropeanSWxcompetencies.We find that the presently ongoing SWx efforts in Europe are to a large degreeuncoordinatedandalsomostlyunsustainable.This isprobablyat leastpartiallydue to thefragmentation of funding responsibilities in Europe. Apart from the ESA and the EU,individualstatesandmanydifferentagenciesalsofundspaceweatheractivities.TheESAispresentlydevelopingpre-operationalSWx-servicesintheframeworkofitsSpaceSituational Awareness (SSA) Programme with 19 out of ESA’s 22 Member Statesparticipating in the SWx segment. However, the ESA SSA programme is optional and theparticipating member-states contribute very diverse voluntary annual contributions, notalwaysreflectingNetNationalIncome.Alsothescopeoftheservices,establishedwithinthisprogramme,iscurrentlylimitedtotesting,verificationandvalidation.The EU had – and still has - scattered H2020 (FPx) SWx calls, reoccurring every other orsometimesevenonlyeverythirdyear.EveniftheEUfundingtoSWxactivitiesaddsuptoaconsiderableamountofapproximately60M€overthelast10years,thefundingofferedineach call is sub-critical to develop sustainable science and service activities, and did notmatchtheEuropeanneeds.Manyof thesecallswere (andstillare)aimedprimarilyat theprototypingofserviceswithrelatively littleregardforthescientific foundations,whicharerequired for suchservices tobecomereliable.Mostof thework required for thescientificunderpinningofSWx,especiallythescienceanddataexploitationactivities(seeourfindingsbelow),fallintothegeneralEU-calls,wheretheycompetewithbasicscience.Additional funding provided by individual European states is fragmented, localised, un-coordinated,andalsomostlyinsufficienttosatisfythegrowingsocietalneeds,forboththeadvancement of knowledge and the provision of services. Also it is difficult to buildtransnationalandregionaleffortsonnationalfunding.Moreover, the private sector is recently becoming more and more active in space, andrealises itsexposuretoSWx-threats.However-andyetagain-thefundingemergingfromsuchsourcesisoftentoodirectedandtopicallyfartoonarrowtosatisfySWxneeds.

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We would like to stress that while this diversity in funding is currently often seen as aEuropeanweakness, itcouldbeturned intoastrength, if itwerecoordinatedaccordingtotheprinciple„Letthosedotheworkwhoarebestatit“.WestronglyadvocateadedicatedEurope-widecoordinationofSWxactivities.ThiscouldbedoneinasimilarmannertohowtheCOPERNICUSprogrammedealswithEarthObservations.CurrentEuropeanSWxservicesrelyondatafromageinginfrastructuresuchasESA‘sSOHOspacecraft, which is rapidly approaching its 25th anniversary, having thus substantiallyexceededitsdesignlifetimeof2years.WhileESAis indeeddiscussingwiththeUSaboutacoordinated development of a common space weather monitoring system, there is noconsolidatedplanyetforthesuccessorforSOHO.Thecurrentscientificspaceinfrastructureisnotabletoprovidenear-realtime24/7operationaldataforfutureSWxwarningsystems.The presently available fleet of space- and ground-based assets, which observe the sun,geospace, and the region of space between these two, the inner heliosphere, offer thecurrent and unique opportunity to increase our scientific understanding of SWx. As thisinfrastructure continues to age beyond its operational lifetime, and given the increasingfunding pressures, progress in the scientific understanding of SWx can, and needs to bemadenow,requiringadequate,coordinated,andreliablefunding.Europe is, of course, not alone in its recognition of the importance of SWx science andservices. European agencies and researchers have long recognised the importance ofinternational coordination of scientific efforts, information exchange on space weatherevents and their mitigation, national, regional and over-regional risk analysis andassessment of user needs. This coordination should be understood to encompass thecurrently scattered,uncoordinated, short-term,andoften insufficient fundingofEuropeanSWx activities and should lead to an increase in funding of SWx activities to a level thatallows an operational European SWx system to be established, operated andmaintained.These activities should cover both the scientific foundations of SWx as well as thedevelopmentandprovisionofSWxservicesforsociety.

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PurposeofthisdocumentTheEuropeanSpaceSciencesCommittee(ESSC-www.essc.esf.org)oftheEuropeanScienceFoundation (ESF) is an independent committee that regularly provides expert advice toEuropeanandNationalresearchfundingandresearchperformingorganisationsthatsupportspace sciences in Europe. Themembers of the ESSC are drawn from experts active in allfields of space research on the basis of scientific expertise and recognition within thecommunity, they are nominated ad-personam and therefore do not represent anyorganisationorcountry.The ESSC covers the whole spectrum of space sciences; it is structured around panels(AstronomyandFundamentalPhysics,EarthSciences,LifeandPhysicalSciences,andSolarSystemandExploration).ThemissionoftheESSCistofacilitateandfosterspacesciencesatthe European level by providing unbiased, expert advice on European space research andpolicyviarecommendationsorreports.Furthermore,ESSCprovidesauniquefocalpointtoassist European national councils and agencies to achieve optimal science return andharmonisestrategicprioritiesinspaceactivities.The ESSC Panel of Solar System and Exploration has in the recent past frequently beenasked to give advise in questions concerning the Policy and Science of Space Weather,which isafastgrowingareaofconcernforourhighlytechnologicalsocietyboth inEuropeandaround theworld. In2015COSPARand the Inter-Agency initiative International Livingwith a Star (ILWS) have published an international roadmap [54] concerning a globalapproach to understand andmitigate effects of adverse spaceweather and to shield oursociety. This roadmap document has ever since been adopted and used as the guiding-document for the planning of a global coordination effort by the Committee for PeacefulUseofOuterSpace(COPUOS)oftheUnitedNations.Ithasalsotriggeredtheformulationofspaceweatheractivitiesandmitigationplansinmanycountries,mostpronouncedmaybeinthe USA in the form of a detailed National Space Weather Action Plan(https://www.whitehouse.gov/wp-content/uploads/2019/03/National-Space-Weather-Strategy-and-Action-Plan-2019.pdf).IntherecentyearsalsomostEuropeancountrieshaverecognisedthepotentialchallengesandriskstoourmodernsociety,potentiallyemergingfromadverseorevenextremespaceweather. Almost every individual country has in some way increased their nationalawarenessandpotentialpreparednessforharmfulSWxeffects.OnEuropeanlevelboththeESAandtheEUarepreparingoverarchingprogramstoincreaseEurope’sabilitytomeettheemergingthreatsfromourspaceenvironment.In response to such growing interest and the increasing international awareness aboutpotentialthreatsfromadversespaceweathertoourmodernsocietytheESSChasbothbeenasked and decided by itself to look into a consolidated advice concerning a EuropeanapproachtoSpaceWeatherriskassessmentandparallelscientificandserviceactivities,bycreatingtheEuropeanSpaceWeatherAssessmentandConsolidationCommittee,ESWACC.The aim of this new Committee was to prepare detailed recommendations for aconsolidatedandstrategicapproachtoSWx-forEuropeasawholeandalsoasapartoftheglobalSWxeffortasadvocatedbytheUN-COPUOS.ThesituationofSWxtodayisthatwedounderstandtheunderlyingprinciplesofSun-Planetinteractions,butwearestillfarfromanoperationalsystemforSWxpredictionsasweknowthemfromEarthweatherforecasts.

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Whileourcommunity is learninghowtomakemoreaccuratepredictionsabout suchSWximpacts,weare–andshouldbe-continuouslylearningmoreabouttheunderlyingphysicsof the coupled Sun-Earth System, in order to improve ourmodels. At the same time thedrivingsocietalneedsareconstantlydeveloping-andchanging.AfutureSWxsystemorservicefunctionneedsbebuiltinawaythatitconstantlycanadaptto such changing requirements. Societal SWx risks – and prediction requirements - aredifferentindifferentEuropeanregions-thusdifferentsolutionswillbeneededfordifferentplacesandalsofordifferentassetsinspaceandontheground.ApromisingapproachtodeveloptherequiredfutureEuropeanspaceweatheractivitiesandservicescanbestbedescribedasaniterativeloop,inwhichthereshouldexistacontinuousiterationandfeedbackbetween:

a) newimprovedscienceunderstandingandsupportingobservationsb) evolvingrequirementsofEuropeanend-usersandinfrastructureproviders,andc) improvedpotentialtodeliverSWxproducts(basedonrecentsciencefindings)

whereb)andc)shouldalsoaddressparticularnationalandtrans-nationalrequirements,andeventuallyfeedbackintonewchallengesforthescienceeffortsundera).

The ESWACChas during the recent two years explored the challenges andmonitored theapproachesbeingtakeninEuropeandaroundtheglobeforadvancementsinSWxresearchand services. In this document the ESWAC-WG has prepared a number of detailedrecommendationsforaconsolidatedandstrategicEuropeanapproachtoSWx,withinwhichwetrytoidentifytheappropriateeffortsandinvestmentsthatneedtooccurinallpartsoftheabovedescribedSWx“iterationloop”inatimelyandcoordinatedfashion.We find thatonecarefullyneeds tobalance long-termeffortsase.g. investments inbasicscience,short-term efforts like investments inapplied scienceand immediate efforts andinvestments in general infrastructure resilience, survival potential and related recoverymeasures.Our recommendations recognise efforts already undertaken by national and internationalorganisations in Europe. The committee has also closely collaborated and coordinated itsactivitieswiththeexistingESASSA-SWEprogramtorecommendapathforwardtowardstheestablishment of a long-term European space weather effort and closely linked tailoredSWx-servicefunctionsforEurope.

1. IntroductionThe impacts of energetic events at the Sun (and outside our solar system) on near-Earthspace - and consequently on technological infrastructure on and around our planet - aregenerallyreferredtoasSpaceWeather (shortSWx).Policy-makers ingovernmentsaroundtheworld are presentlywidely engaged in discussions about the potential risks posed bySWx (see e.g. [36] on recentUNEfforts; or theUS SpaceWeatherActionPlan). Similarlyvariousnationalandinternationalorganisationsareassessingtheadverseimpactsofspaceweathereventsoncriticalinfrastructureandadvancedtechnologicalservices,andwhatkindof information (benchmarks, nowcasts, forecasts) the user communities would require tomitigate space weather impacts. This report focusses on European SWx vulnerabilities,opportunities,andongoingandfutureeffortsrequiredtoreduceEuropeanSWxexposure.

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The socio-economic impacts of SWx events are increasingly being studied in their entirebreadthandintheirfulldepth[45,46];acost-benefitanalysisoftheEuropeanSpaceAgencydetails the importanceofpreparing forSWx1. Suchstudieshaveestablished thatextremeSWx events pose a High Impact Low Frequency (HILF) threat. Such HILF-threats pose achallenge to science to estimate their occurrence rates reliably, and to science, politics,insurance companies, and society as awhole to assess theirpotential damage. Estimatingtheir occurrence rate is crucial because the related damage is potentially so large thatefforts need to be made now to mitigate SWx risks to ensure the well-being of moderncivilisation.Spaceweatherhasnotonlybeenrecognisedasaglobalchallengeforsociety,italsoremainsamajorchallenge for thescientificcommunity itself.While there isaconsiderable,urgentandconstantlygrowingneedtostrengthenthereliabilityoftechnologicalsystemsinspaceand on the ground and their ability to respond to the impact of adverse SWx, there isunfortunately still a considerable lack of essential understanding of the Sun-Earth systemand the very complex and highly dynamic physical coupling between the vastly differentplasma regimes on the Sun, in the heliosphere and in the near-Earth space, i.e. themagnetosphere, ionosphere and upper atmosphere. Of course, it is crucial to understandtheseprocessesifwewanttoprotectsocietyfromthem,butatthesametime,wecannotafford to wait for a complete scientific understanding of SWx before we develop andimplementSWxservicesforsociety.Thusit iscriticaltoensureacontinuingfeedbackloopbetween all SWx actors: scientists, developers, service providers, governments, and endusers.Withthecurrently limitedscientificunderstandingbothofthecausesandeffectsofSWx, efforts today need to focus on how governments should invest into knowledge andmethods to forecast space weather and mitigate its adverse effects in the same way aspolicy-makers invest inmethods tomitigate the risksposedbyothernatural hazards (seee.g.19).WhatmakesSpaceWeatherrisksuniqueisthatthethreatistrulyglobal,affectinglargepartsoftheglobeformajorsolarstormswhilethedetailed impactsvaryat regionalandtrans-national levels.Inotherwords,SWx-eventcanbeverydifferentfromcountrytocountry, depending primarily on the latitude of the country’s geographical coverage,, butalsodependingontheeventitself,onwhetherthelongitudeoftheregionisatnight-,day,dawn-or dusk-side, thedetails of particular vulnerability and connectivity of national and(trans-) regional infrastructures, and the economic interconnections between nations andregions.Spaceweatherisamodernrisk, itaffectsourmodernandinter-connectedsocietyinwaysforwhichwehavenohistoricalexperiencestoteachushowtocopewithit.Spaceweathereventscancreatedamagebeyondtheground-basedinfrastructureintheaffectedregion or country itself by adversely affecting space and aeronautical assets, or otherexternal infrastructure like international transport on water and land. In Europe thisinterconnectedness is complicated by the fact that there are varied national interests,particular vulnerabilities and specific abilities, all of which determine each country’sindividualapproachtoSWx.In this spirit, two European organisations, the ESA and the EU have both - in partnershipwithother globalplayers - recognised the SWx risk for Europeas awhole.But atpresentbothorganisationsareworkingmoreorlessindependentlyinpreparationofinitialEuropeanSWx prediction services as well as trans-national mitigation efforts. Both organisationssupportresearchforanimprovedunderstandingofSWxprocessesandimpacts,andofthe1“Acost-benefitanalysisoftheSSAprogramme”,29September2016.Presentationavailablefrom the Global Space Economic Forum section of the European Space Agency website(www.esa.int/).

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underlying space physics, in addition to, and largely uncoordinated,with already ongoingnational efforts. Moreover, as has been noted before, there are different priorities andattitudestowardSWxresearchandservicesinEurope.Whileresearchfundingorganisationsin some countries prefer to invest in so-called “curiosity-driven” research, others ratherchoosetoinvestinmoredirectedworkaimedatpracticalsolutions.Somecountriesalreadyinvest in both avenues; Space weather is a typical scientific problem area where both –curiosity-drivenandresult-oriented–researcheffortsareneeded.Progress in reducing spaceweather risk for Europeas awhole requires that the guidanceandfundinggivenbytheESAandtheEUarecloselycoordinatedalsowithnationaleffortstoestablishagoodbalanceandsynergybetweenalleconomicandculturalaspects.Thiswouldensure strong links and close connections between efforts funded in Europe and thuscontribute to solutions basedon the particular needs of the European infrastructure, andalsoaccountforparticularEuropeanstrengthsandweaknessesinscienceandtechnology.Furthermoreweshouldnotethattheeffectsofspaceweatherarenotonlyrestrictedtoourownplanet,butdoaffect theentireheliosphere.AsbothEuropeanandworld-widespaceexplorationhasbeenextendedthroughoutthesolarsystem,HeliosphericWeathercanbeathreat foranypresentand futurehumanassetoractivityonotherplanets, for spacecraftorbiting planets, cruising in the wider solar system - or even crossing the boundary tointerstellar space. The protection of these high-cost and high-value assets outside ourclosestgeo-spaceenvironmentisagrowingfuturegoalofSWxactivitiesaswell.1.1. Background-SpaceweatherasaglobalchallengeFollowing the approach defined by the Committee on Space Research (COSPAR) andInternational LivingWithaStar (ILWS)SWxRoad-Mapdocument [54] theeffectsof spaceweatherontechnologicalinfrastructurecanbroadlybedefinedintermsofdifferentimpactpathways:

- geomagnetically induced currents, impacting on power and transportinfrastructures;

- radiationeffectsleadingtoageingandmalfunctionsofspace,aviationandinseverecases even ground assets, including direct impacts on radio wave and othercommunicationtransmissions,

- and combined effects of both radiation and current flow effects, leading toionospheric disturbances of navigation and communication systems, increasedsatellitedragandthusdecreasedsatellitelifetime,aswellasinaccurateassessmentsofsatellites’orbits,whichinturncouldincreasecollisionriskswithspacedebris,asasecondarySWximpact.

Untiltodaythelargestpotentialsocio-economicSWximpactshavearisenfromSWx-drivengeo-magneticallyinducedcurrents(GICs)inelectricalpowernetworks.Examplesincludethevoltage collapse of the Hydro-Québec power network in Canada during a space storm in1989and,morerecently,thefailureofthepowernetworkinMalmö,Sweden,in2003.Themainrisk fromSWxontheelectricalpowergrid isavoltagecollapse (ascausedby lossofreactivepowerand/or trippingof safetysystemsdue toharmonics),whichcanoccurwithonly limiteddamageto infrastructure.HeatingduetorepetitiveGICscan leadtoageingoftransformers as we discuss below. Even more significant and worrying are the potentialdown-stream impacts of such “traditional” SWxeffects,which include the loss of servicesthat rely on the availability of electricity, which, in the interconnected economy of the

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twenty-first century could quickly lead to extreme impacts. Such loss of power can thusresultinextensivedamagetopropertyandinfrastructure,aswellaslossoflife.Thereisalsogrowingevidencethatthecumulativeeffectsofeverydayspaceweather(e.g.lowlevelsofGIC)havesignificantimpactsonelectricpowersystems,impactsthatdegradelong-term economic performance rather than cause short-term disruptions. For example,thereisevidencethateverydayspaceweathercontributestothe“wearandtear”thatlimitstheworking life of transformers [23] andmaybe a significant increase in insurance claimsassociated with failures of electrical systems [53, 54]. There is also a significant body ofeconomicevidenceshowingthatelectricitymarketsareaffectedbyeverydayspaceweather[20,21,22].Today global reliance on space-based assets is rapidly increasing in communication andpositioningservices,aswellasforEarthobservationandalltheirdown-streamapplications.Space radiation during severe space storms can damage satellite systems and even causetheir total loss,either immediatelyat impactoreventually through increasedageing.Eventemporary loss of services from global navigation satellite systems (GNSS) due toionospheric disturbances would have an impact on numerous economic sectors. Aremarkableexample isgivenbytheglobal financialsystemwhichreliesonhighlyaccuratetiming.WhilesuchtimingisoftentakenfromGNSSsignals,mostofthebankingsectortodayis aware of the associated SWx risk and has already developed solutions for these SWx-sensitivetimingsignals.Storm-time ionospheric effects may disturb or even interrupt communications andnavigationsatellitesandhigh-frequencycommunicationsignalsthroughupperatmosphericirregularities in the electron density, which manifest themselves as scintillation andthermosphericeffects,travellingionosphericdisturbancesandionosphericbubbles.Thiscanoccurnotonlyathighlatitudes(intheauroralzoneandnearthepoles),butalsoatmiddlelatitudesandclosetotheequatorasaresultofasolarflareorthedynamicsofionosphericplasmabubbles.Suchdisturbanceshaveimpactsonanyservicesorsafetymechanismsthatrelyonaccuratepositioninformationortheintegrityofcommunicationpathways,affectingfor example airline operations, but also satellite-based augmentation systems, HFgeolocation and communication operations. Space Weather even impacts scientificobservationalsystemssuchastheLOFARandSKAradioastronomytelescopes.Thereisnowincreasing awareness that during quieter geomagnetic conditions, when the Sun is notactive,spaceweatherdisturbancesarestillactive,particularlyatlowlatitude.Forinstance,ionospheric irregularities can be present at anytime, and can impact ground and spacebasedcommunicationandnavigationsystems.Already now and evenmore so in the future, space-basedmonitoring from satellites is acriticalaspectofnumerousEarth-observationapplications,includingmonitoringtheeffectsof global climatic change, for ground- and space-based situational awareness, forcoordinating responses to natural disasters and, more generally, for safety and security.Withtherecentrapidgrowthinthenumberofspaceactorsinbothspace-faringnationsandemergingspacenations,andespeciallyfromtheprivatesector,thereisalsoapressingneedfor increased reliability of satellite-provided services and infrastructure in space and onground. In particular,whenbuilding completely new infrastructure in emerging nations ine.g.AfricaorAsia,oneshouldkeepadverseSWximpactsinmindfromtheverybeginning,and design and construct new infrastructure taking potential SWx risks and their optimalmitigationintoaccount.It is important todevelop scenariosoutlining the likelihoodand the impactof severe - oreven extreme - spaceweather on the Earth andon human activities. An example of how

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vulnerableourmodernsocietyhasbecomeisstudiedbyBakeretal.[6]focusedonthelargeCMEwhichwaslaunchedfromtheSuninJuly2012,andwasdetectedbyNASA’sStereo-Aspacecraft. Those authors found that the 2012 event could have had enormoustechnological impacts on Earth, perhaps even greater than the famous 1859 Carringtonstorm; luckily, the event missed Earth by about a week’s worth of solar rotation. Otherrecent studies [52, 14] found that the likelihood of a similar very severe space storm onEarthinthenextdecadecouldbeaslargeas~3–10percent.Suchrecentstudieshaveledsome countries to develop appropriate national responses to the threats posed by spaceweather,i.e.,tothedevelopmentofappropriatenationalactionplansandprotocolsfortheprotection of critical infrastructure. Because of the global scale of spaceweather threats,such scattered and individual efforts need tobe expanded into awider European contextand eventually into a coordinated global effort. Europe must prepare to contribute andprovideitspartofthatglobaleffort.In summary, our modern society’s strong reliance on technology and its increasinginterconnectedness have significantly increased society’s vulnerability to space weathereffects.Thus, impactsarising fromthenaturalhazardofsevereorextremespaceweatherrequireacoordinatedresponsefromtheinternational(Europeanandglobal)community.Arecentreport fromtheUnitedNationsExpertGrouponSpaceWeather2pointsout thatscientificresearch,detailedsocio-economicandtechnicalimpactassessmentstudiesaswellas preparatory activitieswithin civil protection administrations are needed to ensure thatstatesandregionsknowwhattodotoprotecttheirinfrastructure.Accurateandactionablespace weather warnings are needed so states will know when to act. The new andunprecedented global and interlinked nature of space weather threats means thatauthorities (and thepublic)need toknowhow to act throughnewanddifferent kindsofinformation chains than they have become used to dealing with in traditional civilprotection.1.2. Pastandon-goingEuropeanSWxactivitiesandtheirposition in

theinternationalframeworkThroughouttheentirelastcenturyEuropeanresearchgroupshavedonepioneeringworkonseveralaspectsofSWx, inparticularbydevelopingandutilisingground-basedobservationtechnologies toprobeandunderstandgeo-spacephenomena,mostofwhich todayareofutmostrelevancefordedicatedspaceweatherresearch.Manyoftheoriginaltechniquesarestill at use today both in SWx operations and in SWx enabling science, such as, e.g.,magnetometers, ionosondes and coherent scatter radars,which all havebeen invented inEurope.On the spacecraft side Europe has led a number ground-breaking missions, which havepavedthewaytoourmodernunderstandingofhowspaceplasmaprocessesareassociatedwith and cause space weather. Missions like Helios, ISEE, Ulysses, AMPTE, GEOS, SOHO,ClusterandSwarmhavebeenextremelyproductiveingainingincreasedSWxunderstanding.The first truly three-dimensional 4-spacecraft ESA Clustermission can be considered as apioneeringeffortindesigningaset-upofcoordinatedmulti-pointmeasurementsinspaceat

2 UN Committee of Peaceful Use of Outer Space (COPUOS), Scientific and TechnicalSubcommittee (STSC) Report: Thematic Priority 4. International Framework for SpaceWeatherServices,UN-OOSA,A/AC.105/1171,2018.

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avarietyofscales, incoordinationwithground-basedinstrumentstosupportthescientificprogram,withEarthbeing“the fifth satelliteof themission”.Thesameapproach towardsdedicated ground based instrument coordination has been successfully and formallyadopted later in theNASATHEMISmissionoperation,andhasbynowbecomeaconstantpartofallon-goinggeo-spacemissionsaroundtheglobe.Despiteoftheirvirtuesinscience,noneoftheabovelistedEuropeanmissions(maybewiththeexceptionoftheageing,andnow24yearoldSOHOsatellite)canqualifyasatrue“spaceweatherobservatory”.Noneoftheothermissionsiscapabletodeliver24/7nearrealtimedataabouttheactivitystateorthecompletedynamicsofanyofthecoupledspaceplasmaregimes between the Sun and Earth. Probably this has been one factor motivating ESAmembercountriestoexpandtheagency’sactivitiesfromitsscienceprogram–whichsincelonghasservedastheprimusmotorinSWxexploratorymissions-alsototherealmofmoreoperationalactivitiesundertheauspicesoftheDirectorateofOperations.TheEuropeanSpaceAgency(ESA)startedtheSpaceSituationalAwareness(SSA)Programmein 2009, after the ESA Member States had approved the Programme Declaration in theMinisterialCouncilmeetingin2008.SpaceWeatherisoneofthethreesegmentsintheSSAProgramme.TheothertwosegmentsareNearEarthObjects(NEO)andSpaceSurveillanceandTracking technology (SST). In2009 theProgramme issueda SpaceWeatherCustomerRequirements Document (CRD) that has become the baseline document for thedevelopmentdefiningtheuserneeds.All spaceweatherdevelopmentactivitieswithin theprogramme address the requirements in the CRD and target new capabilities to fulfil theend-user needs. Although SSA is an optional programme, 19 out of the 22 ESAMemberStatesparticipateinthespaceweatheractivitiesintheProgramme.The SpaceWeather System under development in the framework of the SSA ProgrammecomprisesaninitialSpaceWeatherServiceNetworkandthemeasurementsystemsthatareproviding data for the spaceweather services. Inmore detail the SpaceWeather ServiceNetworkconsistsofthefollowingmainelements:

- SSASpaceWeatherCoordinationCentre(SSCC);- FiveExpert ServiceCentres (ESCs) for SolarWeather,HeliosphericWeather, Space

Radiation,IonosphericWeather,andGeomagneticConditions,inBelgium(ROB),theUK(RAL),Belgium(BIRA),Germany(DLR)andNorway(UoBergen),respectively;

- SSASWEDataCentre.In2009–2019theSSASpaceWeatherSegmenthasbeendeveloping,testingandvalidatingtheproductsandpre-cursorservices fromthesystem.TheSSAnetworkofSpaceWeatherExpert Service Centres (ESCs) includes more than 40 Expert Groups representing leadingspaceweatherexpertise inEurope.TheseExpertGroupsareresponsibleforover200dataproducts that are coordinated at the ESC level and combined into 25 precursor serviceswhich are provided to the end users by the SSA SWE Coordination Centre (SSCC). Thisstructure follows the SWE System businessmodel consolidated during SSA Period 3. Theavailablespaceweatherservicesaddresscriticalserviceanduserdomains includingpowergrid operations, aviation, satellite navigation andmanned space flight. All available spaceweatherproductsandapplicationshaveeitheralreadygonethrougharigorousvalidationofthe service content or are in the process of doing that. At the same time developmentactivities for new capabilities focussing particularly on improvements in space weathernowcasting, forecasting andphysics-basedmodelling are being carriedout. Themodellingactivities in 2016-2019 have particularly been focussing on forecasting of solar flares,heliosphericmodelling andMHDmodelling of the solar wind interactionwith the Earth’smagnetosphereandupperatmosphere.SpaceWeatherESCsarecontinuouslyengagingwith

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the European end users to test all space weather products and service elements and tocollectfeedbackforcontinuouselaborationoftheuserrequirementswithintheProgramme.ThemeasurementscurrentlyutilisedbytheSSASpaceWeatherSystemcomefromscienceand technology demonstration missions (e.g. SOHO, ACE, Proba-2), ground basedmeasurementsystems(e.g.theMIRACLEnetwork,networksofGNSSreceivers,ionosondes,neutron monitors, etc.) and operational space weather monitoring missions (e.g. GOES,DSCOVR).TheProgrammehas launcheditsfirsthostedpayloadmission inDecember2018(SOSMAGmagnetometeronboardGEO-KOMPSAT-2Asatellite)andthesecondmissionwillbe launched in July2019(NGRMradiationmonitoronboardEDRS-C) (formoredetailsandaccesstotheSWxdatayoucanregisterforSSAat:http://swe.ssa.esa.int/web/guest/asset-database)To further ESA’s contribution to the expressed European goal to “ensure Europeanautonomy inaccessingandusingspace inasafeandsecureenvironment”,ESA intends toputforwardanoptionalSpaceSafetyProgrammeatthenextCouncilmeetingatMinisteriallevel in November 2019. The new programme will be addressing the three segments of:Spaceweather;Planetarydefence;andDebrisandCleanSpaceandbuilduponthesuccessofESA’sSSAProgramme.SpaceWeathersegmentactivitiesintheSpaceSafetyProgrammewillcontinuedevelopmentoftheSpaceWeatherSystemincludingspaceandgroundbasedmeasurementsystemsandnetworkingofEuropeanspaceweatherassetsandexpertise.TheSpace Safety Programme will also continue the elaboration of the European end userrequirementsandsupport infrastructuresensitivity studies includingaspaceweatherCostBenefitAnalysis(CBA).ThestartupoftheESASWxprogrammeisaverypromisingdevelopment,butwestillseemto struggle with several Europe-specific obstacles hampering fast and further progress.WhileEuropeanresearchinstitutesare,indeed,buildingandrunningseveralinterestingandimportant observation programmes for upper atmospheric andmagnetospheric research,directlyorindirectlyenablingthefuturedevelopmentofspaceweatherservices,wehavetoacknowledge the fact that the North American countries and Japan are today ahead ofEuropeinthecombineduseofgroundandspaceexperimentsforaholisticviewonspatio-temporal evolution of spaceweather phenomena. It seems that the traditional Europeanapproach, where ground-based observations are funded in national programs and space-basedmissionsby separatemulti-nationalprogrammesorbyESA, isnotas favourable formodern coordinated measurement concepts as some other non-European nationalprogrammeshavebeen.Asmanyemergingcountriesarepresentlymakingfastprogressinthefieldaswell,Europeshouldtakepromptactionformoreagile,coordinatedobservationprogrammesinordertomaintainitspositionasacredibleand-moreimportantly-reliablepartnerinleading-edgespaceweatherenablingresearch.Major efforts to establish a permanent SWx monitoring function in parallel to theexploratoryscientificfleetofheliophysicsmissionsareatpresentmoreorlessrestrictedtotheUS (NASAandNOAA).When it comes tomore global coordinationof “spaceweatherenablingscience”missions,theInternationalLivingWithaStar(ILWS) initiativehasforthepast 10-15 years paved theway for a continuous scientific gap analysis and has fosteredinternational partnership in enabling science missions for growing space weather needs.However, there is still no truly global process to coordinate SWx missions of differentagencies around the world into one future global space weather programme, with 24/7observational capabilities in the prime regions and regimes of space weather processes.There is ample room and reason to continue global international partnerships (asdemonstratedbytheILWS)alsoformissionsmeetingmoreoperationalSWxneeds.Europe

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shouldexpress itsambitionandconsequentlystrivetobecomea leadingpartner insuchafutureglobaleffortonSWx.The presently on-going discussion between ESA and NOAA to place two coordinatedmonitoringmissionsatboththeL1andL5pointsisagoodstartofsuchglobalactivities,butbeyond these primary near-Earth monitoring points there are strong requirements forcoordinated observations both closer to the sun and atmany locations in Geospace. Theentirefleetofrequiredspacecraftforaglobalspaceweatherservicewillgofarbeyondthecapabilitiesofanyonespaceagency intheworld.ThusEuropeshould, inpartnershipwithother agencies, agree to supplymissions and assets to a global network, keeping inmindbothEuropeanexpertise,capabilitiesandrequirements.ThusanyEuropeanactivitiesinthisfield should be seen as part of a global effort. This approach has particularly beenemphasised in the ILWS/COSPAR Space Weather Roadmap [54], which has consequentlybeen adopted as the baseline for global space weather efforts as pursued and closelymonitoredbytheUN-COPUOSExpertGrouponSpaceWeather.Any such futureEuropean contribution to futureglobal SWxefforts shouldalso reflectonhow economic interconnections will make most countries vulnerable to space weatherimpactsonotherpartsof theworld, i.e., that thereare significantmutualbenefits arisingfromglobal cooperation in spaceweather riskmitigation.Wenote that theSWxroadmap[54]mostlyaddressessuchglobalactivities,andwhile itmayneedtobeupdated insomeparts, we nevertheless consider it a good starting point for a tailored European plan forsustainablespaceweatherresearchandoperations.Therefore,ourrecommendationsbelowareinmanycasesbasedontherecommendationsoftheroadmap.On a separate website (http://www.essc.esf.org/studies-and-publications/eswacc-report)we have compiled – to the best of our knowledge – a present day description of andreferencetopastandon-goingEuropeanSpaceWeatheractivities, fundedbyESA,EUandnationalmemberstateorganisations.

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1.3. OtherRemainingChallengesIt is important tokeep theentire coupled systemof solar terrestrial events inmindwhenanalysing SWxprocesses.Muchof the radiation originating fromSolar Flares andCoronalMassEjections(CME’s)reachesEarthwithinafewminutes,introducingmostlyionosphericandatmosphericeffectsandconstitutestheRadiationandSEPpathwaysofSchrijveretal.[54]. However, the CME pathway has a different temporal characteristic, as it takes theplasma cloud and the surrounding magnetic field structure about 1-3 days to propagateformtheSun toEarth.Onlyuponarrivalof theCMEat theEarth’soutermagneticbarrierdoes the interaction of the disturbed solar wind with the Earth’s magnetosphere start awhole chain of coupled processes of storage, transfer, and release of huge amounts ofenergy (see details below). Further complications come from the interaction betweenelectricallychargedandneutralparticlepopulationsintheatmosphere,whichappearsasamyriad of chemical reactions and waves affecting particle densities, temperatures andvelocities. Planetary waves, tides, and gravity waves propagate upward from the loweratmosphere, deposit momentum into the mean thermospheric circulation, and generateelectric fields via the dynamomechanism in the lower ionosphere.Dynamoelectric fieldsare also created by disturbance winds. Neutral winds and electric fields from thesecombinedsourcesredistributeplasmaoverlocal,regional,andglobalscalesandsometimescreate conditions for instability and production of smaller-scale structures in neutral andplasmacomponentsofthesystem.Theabovedescribedcoupledinteractionsoftheentire“Geo-spaceSystem”ispresentlynotunderstood in sufficient detail to predict the time and location of those very strongdisturbancesinupperatmosphericelectrodynamics.Weonlyknowthatmajorcomplicationsin ground and space-based technology may happen, with a short advance notice of fewhours.WhilewedounderstandenoughaboutthephysicsofthecoupledSun-Earthsystemtoknowwhatkindofdisturbancescanandwillfollowfromacertainspaceweatherevent,we are still far from being able to predict the “where and when” and the “how bad” ofevery consequentdisturbance.Dependingon the rotation-positionof theglobeunder theday-andnight-sideofthemagnetosphereanyerrorinthe“when”willshiftthe“where”byan amount larger than the longitudinal extentof some countries or even continents.AlsothedegreeofmagneticcouplingbetweenthesolarwindandtheEarthsmagnetospherecanshift theauroralzone in latitudebymorethan500kmand insomecasesevenmorethan1000 km. As we often will not not know which latitudinal and local time areas will besuffering from any such SWx impacts, the value of any detailed regional warnings maybecome compromised. The resulting narrower forecasting window may then not besufficientfortheuserstodevelopefficientmitigationprocedures.

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2. FindingsandRecommendationsThechallengesstatedabove,whichareimposedbytheSun-Heliosphere-Geospacesystemitself, imply the following basic and overarching principles of a future European SWxarchitecture-yet-to-be-developed:

- Predictionsofspaceweathereventsrequireadeepunderstandingoftheunderlyingscience and rely on the availability of a variety of different - often scientific -datasets.Thesedatasetsneedtobecombined,modelled,analysed,andassimilatedinto networks of models and datasets. This complex flow needs to be constantlyimproved.

- ObservationsandtheprocessingofcorrespondingandotherrelevantdatafromSuntoEarthmustbeavailableinnearrealtime.

- Coordinated observing capability between all space- and ground-based monitorsmustbeimproved.

- Regionalground-basednetworksofsufficientstationdensityneedtobecoupledtoallow the understanding, now-casting, and prediction of - amongst others -magnetospheric disturbances (substorms and spikes in storms) and ionosphericirregularities (scintillations, sporadic E layers, travelling ionospheric disturbances)thathaveamostlyregionalimpacts.

- Instrumentsforobservingtheupperatmosphere,magnetosphere,heliosphereandthe sun need to be calibrated and inter-calibrated, to enable both long-termobservations and intercomparability. This recurring activity requires coordinationandoversight.

- Standardisedprocedures fordataarchiving,preservationandopenaccessneed tobedevelopedandimplemented.Thisalsoappliesmodelsandmodelresults.

- ModellingofSWxphenomenaneedsaverystrongeffortonthephysicalinteractionsand feedbackmechanisms in theSun-Earthsystem inacoordinated,andcoherentmanner.

- Such modelling should cover not only the Earth-Sun system, but also the innerheliospheretoallowbettervalidationbyusingmeasurementsbyexistingandfuturedeep space missions and to support (and prepare for human) exploration of thesolarsystem.

InthefollowingwewillpresentourdetailedfindingsandmakerecommendationstomeettherequirementsforanimprovedEuropeanspaceweatherprogram-structuredundersixmainthemes,whichwerealreadyintroducedinthepreviouschapters:

• Area 1: Imminent Need for Critical Research with Dedication to Enable SpaceWeatherUnderstandingandPrediction

• Area 2: Support to system-science approach with Coupled Physics-basedModelling:Sun/SolarWind/Magnetosphere/Ionosphere/Atmosphere

• Area3:ConsolidationofNational,RegionalandEuropeanRiskAssessments• Area4:ConsolidationofEuropeanUserRequirements • Area 5: “R2O” and “O2R” or how can SWx scientists interface with candidate

organisationsforSWxservices–inEuropeandglobally• Area 6: Define and implement a network of space and ground-based assets for

futureSWxobservations

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2.1. Area1: ImminentNeed forCriticalResearchwithDedication toEnableSpaceWeatherUnderstandingandPrediction

Ascience-drivenapproachtothemitigationofspaceweathereffectsincreasesconfidenceintheassessmentsofriskandsocio-economicimpactsandintheaccuracyoftheirresults.Asdiscussed, for example, in the COSPAR/ILWS roadmap [54], and despite very significantrecent improvements in the understanding of the drivers of extreme space weather,scientistsarestillalongwayfrombeingabletoofferhighqualityforecastingofimpendingseverespaceweatherthatprovidesconcretebenefitstousers.ThecomplexityofSWxphenomenahasledtoadistinctionbeingmadebetweenhighqualityforecasting and high precision forecasting. SWx forecasts need to distinguish betweenamplitudeandtimingofthephenomena[49],especiallybecausetheubiquitousprocessofmagneticreconnection,whichunderliesmuchofSWx,ishighlyunlikelytobepredictableinthedeterministicsense.Whilehighprecisionprobabilitiesoftheamplitudesofsucheventsmaybepossibleinthefuture,wedonotexpecttobeabletopredicttheironsettimesareinthe coming decades [48, 29]. We may ultimately have to embrace uncertainty as afundamentalpartofspaceweatherforecasting(seealso[44]).Findings:Research in the past decades has led to substantial progress in our understanding of theoverallbigpictureoftheSun-EarthSWxchain.Nevertheless,thisresearchhasalsotaughtushow complex and interconnected the Sun-Earth system is. At presentwe still lack criticalunderstanding of: the solar activity cycle itself, of the origin of solar eruptions, of howheliospheric transients propagate into, interact with and, evolve in the solar wind, thedetailed mechanisms of energy storage, transformation and release in themagnetosphere/ionospheresystem,andofhowthisisreleasedintotheatmosphereandtheEarth’s conducting crust. This insufficient understanding currently limits our capability tomeet the expectations emerging from most present – and still increasing - userrequirements.The network of space- and ground-based assets, which formed the basis for our presentscientificunderstandingoftheSWxchain, isageingandindangerofturninginsufficienttoprovidethereliable inputneededforarealisticoperationalSWxsystem.Despitethe largevisibility in thepublicof space-basedassets, atpresent there is no indication thatwewillhaveasimilar fleetofspacecraftatourdisposal inthenear future.Networksof themuchless prominent ground-based stations are presently operated on decreasing, oftenuncoordinatedandunstablenationalor even institutionalbudgets. Suchnetworks requiretheeffortsofscientistsandengineersfortheircontinuedmaintenancethroughgrass-rootsefforts, which in many cases is becoming ever-more unsustainable. Nevertheless, mostpresent-daySpaceWeatherservicesrelyonsuchnetworks,whichmaysuddenlydisappearwith a loss of their funding. Examples of such networks aremagnetometers, geo-electricfield sensors, ionospheric radars, optical imagers, ionosondes, multi-frequency radio-observations of the sun, solar imaging (in the visible, and H-Alpha) as well as neutronmonitors,observationsofradio-scintillationandFaraday-rotation inthesolarwind,andsoon.Toachieveanoptimumexploitationofspacesciencedatafromexistingspaceassets itwillfurthermorebenecessarybothtomaintaintheexistingcoverage-andtoclosesomeglaringgaps-ofpresentdayground-basedspacescienceobservinginstrumentnetworksinEurope,aspartofaEuropeancontributiontotherequiredglobalnetwork.

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Furthermore,attheEuropeanlevel,welackacoordinatedefforttocombinetheresultsofpast,ongoing,andfutureSWx-enablingresearchintoaSWxpredictionframework.Wealsolack a coordinated European science effort to combine the results of individual SWx-enabling research activities. On a global scale this is presently attempted by the COSPARPanelforSpaceWeather(PSW)throughtheestablishmentofso-calledInternationalSpaceWeatherActionTeams(forI-SWATseehttps://ccmc.gsfc.nasa.gov/psw/)The “Bureaucracy Load” presently existing at both ESA-SWE and the EUH2020 grant andprojectmanagementisveryhighespeciallyforuniversityscienceleaders.ESA,andtosameextent theEU,need to recognise that such leadersof science teamsaregenerallydirectlyinvolvedinthescientificworkofthestudiesfundedbyESAandtheEU.Unlikein industry,there is not a separate layer of management in scientific institutions. The contractmanagementprocessforscienceteamsneedstoreflectthis,strikingabalancebetweenthatprocessandtheneedtomakescientificandtechnicalprogress.Scienceleadersneedtimetodo their scientificworkbetweenprojectmeetings and reporting.A failure to respect thatwill divert already scarce resources away from scientific work and is likely to delay theimportantprogressintechnicalandscientificprogress.GeneralRecommendationsforArea1:

1. Sustained and adequate financial support to a directed SWx-enabling researcheffort insolar,heliosphericandmagnetospheric/ionospheric/atmosphericphysicstobuildabetterknowledgebaseforfutureSWxservices.

2. Exploitation of existing SWx datasets fornearGeo-space (e.g. SWARMandother

LEO andGEO satellites,…), in themagnetosphere (e.g. Cluster, Themis,MMS, VanAllen Probes,…), in the Heliosphere and for the Sun (e.g. SOHO, ACE, Wind, SDO,Hinode, Parker Solar Probe,…) should be lifted out of future general H2020 dataexploitationcallsbycreatinga"dedicatedfundingline"forspaceweatherenablingscience,withthedeclaredgoaltoimproveSWxforecastreliabilityandinordertostimulatethe"harvestingoflowhangingfruits”!

3. Efforts to combine data and results from connected regimes (system science)

shouldbeencouraged.

4. Anysuch funding shouldbeona long-termand regular,andcontinuousbasis tomakebestuseoftheEuropeanassets.

5. FostercollaborationbothwithinEuropeandwithsimilareffortsaroundtheworld.

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AdditionalRecommendationswithrespecttoground-basedefforts:

6. Dedicated and, if at all possible, coordinated financial support, both at nationalandEuropeanlevel,toground-basednetworkeffortswhichsupportSWx-enablingresearch in the physics of the Sun, heliosphere, magnetosphere, ionosphere,atmosphere, and solid Earth physics in order to build a better knowledge base forfutureSWxservices.Thissupportisneededforthecontinuationandmaintenanceofsuchnetworksandtoclosegaps.

7. Encouragememberstatestoseefundingofnationalinstrumentassets(oftenparts

ofnetworks)asaglobal subscription foraccess toalldata fromwiderEuropeanandglobalprogramsofsimilarinstrumentsandasacriticalnationalcontributiontoawiderandimportantpan-EuropeanSWxobservingnetwork.

8. Efforts should be supported to combine and coordinate any European assets

concerning such instrumentation into regional and global networks, to enableimprovedcollaborationanddata-sharingwithotherspace-basedSWxassets.

9. Itisimportanttodecreasethe“BureaucracyLoad”presentlyexistingatbothESA-

SWEandtheEUH2020grantandprojectmanagement.Oneofourrecommendationsaboveaddressestheterm“lowhangingfruits”,bywhichwemeanoutstandingscientificquestionsofSWx-enablingrelevancethatcouldandshouldbeaddressed nowby utilizing past and present data and information fromexistingmissions,instrumentsandmodels.Aunique-albeitsomewhatageing-fleetofspacecraftispresentlyobserving the Sun, the solar wind and the near Earth environment and a globe-spanningnetwork of ground-based instrumentsmeasures the impacts of SWx on Earth.We doubtthat such an opportunity for frontier-advancing science including severalmulti-spacecraftmissions, andwell-developed ground-based networkswill re-occurwithin the foreseeablefutureofSWxobservations.Thisoffersauniqueopportunitytocombinebasicandappliedscience efforts for the benefit of knowledge advancement in SWx science. SimilarapproacheshavealsobeenrecommendedintheUSNationalAcademy2013-2024DecadalSurveyforHeliophysics(2012).In the next paragraphs we will, for each regime, summarise some of the most urgentscientific questions concerning the fundamental physical processes that cause extremespace weather and how they could be addressed in a timely manner to advance ourknowledgeabouttheprocessesunderlyingSWx.SunSpaceweatherphenomenaarestronglyrelatedwiththesolardynamo,whichgeneratesthevariable magnetic field of the Sun. This variability is characterised by the 22-year solarmagneticcycle thatmodulates thenumberof sunspotson thesolardisc.Higherup in thesolaratmosphere,inthesolarcorona,groupsofthesesunspotsarepartofso-calledactiveregions, composed of predominantly closed magnetic loops that connect sunspots ofdifferent polarity. In “coronal holes” the magnetic field expands outwards and fills andstructuresinterplanetaryspacewiththe(fast)solarwind.TheSunrotatesarounditsaxisinroughly27daysasseenfromtheEarth,withthesolarpolestakingafewdayslongerforacompleterotationthanthesolarequator.Followingthisrotation,themagneticfield,whichis imbeddedinthesolarwindissweptaroundmuchlikefire-hosestreams.ThesolarwindfromsimilarsourceregionspassesbytheEarthwitha27-dayrecurrence.

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Thesolaractivitycycleisdeterminedbytheconcurrentinterplayofthedynamomechanism,the latitudinal and radial differential rotation and the inner meridional plasma motions,whosedynamicsaredifficulttomodelandpredict.Thechaoticbehaviourresultingfromthecombinationoftheseprocessesmakesitimpossibletopredictbothsunspotemergenceandclustering, as well as the sunspot group magnetic topology and evolution. In turn, thisaffects thepossibility topredictwhether,whenandhowanactivitycentrewill flare,whatwill be the outcome, and the energetics to be expected.With increasing complexity, themagneticactiveregionsinthesolarcoronatendtobecomeunstabletoso-calledmagneticreconnection, leading to energy release in terms of particle acceleration and heating,producing energy emissions, called solar flares, which are observed over the entireelectromagnetic spectrum.Solar flaresarecategorised,e.g.,according to theiremission insoftX-raysusingalogarithmicscaling.Themostviolentclassofflares(X-class)amounttoanincreasebyafactor10000insolarX-rayemissionwithrespecttothebackgroundlevel(A-class) observed on quiet days. The samemagnetic instability process can lead to coronalmassejections(CMEs)wherebyalarge(typically1012kg)volumeofgasisexpelledfromthesolaratmosphereintothesolarwind.IfthepropagationoftheCMEisfasterthanthatoftheambientsolarwind,thentheCMEfrontscansteepenintoshockwaves.CME’sareextremelyvariableinallproperties(magneticfield,plasmadensity,mass,sizeandvelocity).ThisresultsinawiderangeofeffectsonGeospace,frommainlycausingbeautifulaurorasinmildeventstodevastatingimpactsontechnologicalinfrastructureinrareextremeevents.InthewakeofsolarflaresorCMEshockwaves,solarplasmaparticlescanbeacceleratedtonear-relativisticspeeds.TheparticlesescapeawayfromtheSunintospace.Movingthroughspace, theseelectricallychargedparticles (electrons,protons,andheavier ions)are forcedto followthemagnetic fielddragged intospaceby thesolarwind.These fastparticlesarecalled‘SolarEnergeticParticles’orinshortSEPs.Theirvelocitiescanapproachthespeedoflight, theirenergycanbesufficient topenetratespacecraft,affectelectronics,and lead toaccelerated aging of space assets. They can be critical formanned spacemissions, and inrarecasestheycanevenreachandaffectinfrastructureontheEarth’ssurface.In recent times,many techniques, includingmachine learning, have been applied to flareforecasting,but theconfidence levelof the results is stillunsatisfactory fora reliableSWxpredictionchain.Notwithstandingthecontinuoussearch foreffectiveprecursors,very fewof them have been identified and their statistics are not robust enough (e.g., sigmoidalconfigurations,pre-flaremicrowaveemissions,etc.)forforecastingpurposes.Similarly,onlynow-casting is possible for prominence eruptions that lead to CMEs. Furthermore, it isdifficulttopredictthemagneticstructureandpolarityofCMEs.Remarkably,eventheexactrelation between flares and CME’s is presently unclear. In addition, the formation andevolutionofthesolarwindfromcoronalholesandotherregionshasnotbeensuccessfullymodelledtodate.The Sun thus drives space weather with its 27-day rotation, coronal holes, and withirregularlyoccurringeventssuchasflares,CMEsandSEPs.Itsactivityvarieswithanoverall22-year magnetic cycle, which in turn is modulated by longer-term cycles of stronger orweakermaxima.Since the launch of SOHO (1995, ESA/NASA), significant advances have been made inunderstanding how these solar signatures and events propagate throughout theheliosphere.Contemporaryandupcomingsolarmissions inspace (NASA’sSDOandParkerSolarProbe,ESA’sSolarOrbiter)andobservatorieson theground (DKIST,EST)promise toshedlightonthemanystillopenquestions,suchas:

- How does the solar dynamo work and can we understand the variations in themagneticfieldandtheirconsequences?

- Canthestrengthofthenextsolarmaximumbepredicted?

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- Cantheemergenceofcomplexactiveregionsbeanticipated?- Howcanwemeasureand identifymagnetic instabilities inthesolarcoronabefore

theyeruptasflaresorCMEs?- Why is there a corona at all and what are the respective roles of nanoflares,

turbulenceorwavesintheheatingofthecorona,andhowcanthisbepredicted?- Howisthecoronaconnectedtotheheliosphere?Wherearethefootpointsonthe

solar surface of the heliosphericmagnetic field lines?Where does the solar windcomefrom?

HeliosphereTherearestillanumberofunsolvedproblemsinourunderstandingofthedevelopmentofaCMEonitswayfromejectionattheSunto1AUorrathertheEarth-SunLagrangePointL1.RemotesensingobservationsfromL1donotgiveaverygoodpictureoftheCMEgeometry(only the CME “halo” is visible), and thus the initialisation of the CME structure and itsejection velocity can generally not be included correctly in state-of-the-art models andassimilations. In addition the development of both the CME and the shock driven by itstronglydependson theCME itself, and the solarwind, throughwhich the InterplanetaryCME(ICME)hastomakeitswaytowardsEarth.Thustheinternal(magnetic)structureoftheCMEandthestructureofthebackgroundsolarwindhaveanimportantimpactonestimatesofICMEarrivaltimeandstructureatL1.Multi-viewpoint satellitedata (ase.g. fromSTEREO,VEX,MESSENGER,MAVEN,etc.) couldhelp a lot to improve our knowledge and understanding of the 3D geometry andpropagation behaviours of ICMEs, however, there are stillmany parameters that are lesswellcovered,whichpreventsusfromimprovingforecasts.ThebasicquestionifaCMEhitsEarth or not is to know the directivity of a CME. Aswe observe a line-of-sight integratedintensity from imagedata,even thoughhavingmulti-spacecraftdata, thedirectivity is stillstrongly affected by uncertainties. The propagation direction has large impacts onestimatingtheactualarrivaltime,impactspeedandgeomagneticeffects.CMEflankhitsareusuallyrelatedtomilderSpaceWeathereffectscomparedtoapexhitsasthecompressionof themagnetic field is strongest at theCMEnose. In general, single events are easier toforecastcomparedtomultipleevents,whichleadtoCME-CMEinteractions,orinteractionsof CMEs with large-scale structures in the solar wind such as stream interaction regions(SIRs). A series of recent studies concerning the so called 2015 St Patrick’s Day storm(“GeospacesystemresponsetotheSt.Patrick’sDaystorms in2013and2015”, JGRspecialsection, Febr. 2016) give evidence that multiple, interacting or combined events may bemoreeffectivedriversofsevereSWximpactsatEarth.ToforecastthearrivaltimesandspeedsforthoseCMEsthatareidentifiedtopossiblyhittheEarthmagnetosphere,weneedtoderivethedragforceactingonit.ThedragforceactingonanICMEininterplanetaryspace,asweunderstandittoday,mainlydependsontherelativespeedbetweentheICMEandtheambientsolarwind,andtheirrelativedensitiesaswellasthesizeoftheICME.Thisimpliesweneedtobeabletosimulatethebackgroundsolarwindstructures (especially high-speed solar wind streams) and their characteristic parameters.There are only few observational data points available for solar wind parameters ininterplanetary space: Only very few spacecraft at extremely scarce selected positions canmonitor the in situ solar wind; from Earth, interplanetary scintillation (IPS) radiomeasurements are sometimes available from e.g. EISCAT and LOFAR, but only cover theplaneofthesky.LOFARmaybecomeavailablemorecontinuouslythrougharecentlyfundedEUH2020 funded project, LOFAR4SW. For a general assessment of current capabilities topredictCMEarrivalseee.g.[31].

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Basedonsuchobservationswearecurrentlyabletomodelthesolarwindspeedtoacertaindegree of reliability, but other parameters, above allmagnetic field, but also density andtemperature are notwell understood in order to successfully drive physics-basedmodels.Furthermore,weneedtohavebetterestimatesofICMEdensity,hencemass,andabetterunderstandingofhowthemassisdistributedwithintheCME,andhowitevolvesastheCMEpropagatesininterplanetaryspace.Moreover,wealsoknowthatinourappliedapproachofMHD drag, currently the magnetic field, which is supposed to have effects on thepropagationofaCME,isnotatalltakenintoaccount.Infact,themagneticfieldtopologyoftheICMEitselfisanotherissue,representingthe“holygrail” in solar and heliospheric physics. The magnetic field of the CME and all relevantmodelsforheliosphericsimulationsareto-datefedbyasinglemagneticfieldmeasurementtakenatthephotosphericlevel.Thecoronalfield,infact,theatmosphericlayeroftheSunthatactually is themajorcomponentofaCMEeruption, cannotyetbemeasured,even ifeffortsareunderwaytoachievesuchmeasurementinthefuture.Usually,modelsareusedtoestimatethemagneticfieldinthecoronaandalsoininterplanetaryspace,implyingmanyassumptionsbecauseofmanyunknownparameters.Thusweseethat,basedoncurrentobservationaldataandcomputationalmethods,wehaveto accept large uncertainties in our predictions at the level of around 12 hours [42]. Thiscould,however,beconsiderablyimprovede.g.byanadditionalsolarwindobservingassetatL5.TechniquestohandleuncertaintiesinIMFforecastsviadownscalingarebeingdeveloped[see47].Apromisingapproach to improvepredictionsdespite these largeuncertainties istheuseofso-calledensemblemodels[1,48].Ratherthangivingabsolutevaluesforarrivaltimes, impact speeds, etc., probabilities can be given for parameters that cause SpaceWeathereffects.Suchensemblemodelsrunmanysamplesof inputdatasets,whichcoverthe existing uncertainty margins. They require substantial computational power and theappropriate IT-infrastructure [seee.g., 40,48,1]. This isnotaffordable forevery scientificresearchgroup.CommunitycentresliketheESA/VSWMCinBelgiumortheNASA/CCMCstillrequirebetterandmorecontinuousfinancialsupportandclosercollaborationtoprovideaplatform for models to be tested and actually used. Such platforms can also potentiallybecomethe futuredriveway forR2Oactivities (seeChapter2and5),wherescientistsandusersmeet.Wehaveidentifiedmostpresentgapsinourobservationaldata.Closingthemshouldleadtoground-breaking scientific results, which in turn will feed into improved operational SWxservices. Most of the instruments needed for measuring the coronal or interplanetarymagnetic field have already been described in the scientific literature. The necessarynetworksof ground-basedobservatories forH-alpha, IPS, and radiowaveshavealsobeenclearly identifiedandtheydoexist in initialstages.For instance,LOFAR4SW,anEU/H2020project,isapromisingfirststep.Onthedownside,westillrequirecontinuedandsufficientfinancial support for these identified needs. History has taught us that we can maketremendousprogressbycombining theorywithobservations, long-termobservationswithscience,andthatthisisdrivenbynewinstrumentsaswellasnewmethods.Keytopicsthatneedtobeinvestigatedusingpastandpresentground-basedandsatellitedata:

- Improvemodels of the structured background solar wind to derivemore reliableforecastsforCMEpropagation.

- Derive better 3D estimates of CME geometry and mass that both strongly affectICMEarrivaltimeandimpactspeed.

- Reliably connect observational/modelling results for magnetic field orientation attheSunwiththosemeasuredinsitu.

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- UnderstandhowtheinteractionbetweenIMFandCMEchangesthemagneticfieldandwiththatthegeo-effectivenessofICMEsandtheirsheaths.

- Effectively connect and exploit data of existing networks of ground basedobservations(e.g.,magnetographs,H-alpha,IPS,radio,…)andsatellitemissions.

MagnetosphereOncethesolarwind(beitintheformofnormalvariablesolarwind,Co-rotatingInteractionRegion (CIR), or ICME) reaches the terrestrial bow-shock andmagnetopause, it begins toinfluence and modulate the coupled system of plasmas in the various regions of themagnetosphere and upper atmosphere. These interactions often appear as plasmawaveswith great variability in their properties and propagation paths. We have a basicunderstandingofthefundamentalprocessesbywhichenergy istransferredfromthesolarwindintothecoupledgeospacesystem.Thesamemayalsolargelybesaidfortheprocessesthatcontrolthesubsequenttransport,storage,andreleaseofenergyinthecoupledsystem.This knowledge has in general been derived using normal solar wind fluctuations; forexample the processes active inmagnetospheric substorms have been studied intensivelyforover50years.Nevertheless,theexacttimingandmagnitudeofsporadicandveryrapidnight-side magnetospheric energy releases remain unclear, and only the directly drivenmagnetospheric processes are reasonably well understood and thus to some degreereasonably predictable. Also the main features in the statistical occurrence of differentplasmawavesinvariousmagnetosphericregimesareknown,buttherearestillmanyopenquestionsintheinteractionofdifferentwavemodesandtheirlinkagewiththedynamicsofelectric currents and particle populations. Fundamentally, how these multiple processescombine and couple together in the global system is still poorly understood. Since theseprocesses are also tightly coupled, the result is that it remains extremely challenging toaccuratelypredicttheoverallresponseofthecoupledsystemtoincomingsolarwinddrivingconditions, even if the characteristics of the upstream solar wind drivers are knownperfectly.Toalargedegree,thelargerandmorelong-lastingthedriving,themorecomplexandun-predictabletheoverallresponseofthecoupledsystembecomes.Both sporadic and directly driven processes and the relatedwave activity are all stronglycoupled to the ionosphere below. During extreme space weather the resulting so-calledgeomagneticstormscontainayetunknownmixtureofdrivenandsporadicenergycouplingprocesses,whichmakestheentirepicturehardtobothunderstandandpredict.Statisticallywedounderstandhowmultiplesubstorm injectionsbuildupthe largestormtimecurrentsystems and populate the energetic particles in the ring current, how the auroral zonemoves tomuch lower latitude, and how the overall growing auroral andmagnetosphericcurrent systems connect to the ionosphere below, causing detrimental SWx effects ontechnologicalinfrastructure.RecentNASAmissionsinthenear-EarthspacesuchastheVanAllenProbeshaveenhancedourunderstandingonwave-particleinteractionsassourcesandlossesforparticlesinthenear-Earthmagnetosphere.Similarly,theNASAMMSandTHEMISmissions, and the ESA/NASA Cluster mission, have all improved the process levelunderstandingofmanyaspectsofsolarwind-magnetospherecoupling,andnightsideenergytransport and release during storms and substorms. With their advanced and high-resolution instrumentation thesemissions are able to providemore versatile informationthan their predecessors, but unfortunately the system level response is still poorlyunderstood. The understanding of extreme conditions is also hampered by the fact thatmorerecentlylaunchedmissionshaveyettoexperienceextremelystrongstormconditionsduetothecurrentrelativelyquietofsolarconditions.Wehavesofarmuchlessknowledgeabouthowthesystemrespondstoextremesolarwinddrivers,asotherinstabilitiesmaybetriggeredinextremeconditionsandthecoupledsystem

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mayrespondnon-linearlytosuchdrivers.Substorm-likefeaturesdostillexistinstorms,butareknowntobehavemuchmoreerraticallyandalsomoreviolentlyduringmagneticstorms.Via extremely localised short-lived three-dimensional current systems, consisting of bothfield-aligned magnetospheric currents and ionospheric currents, such sporadic energyreleasescausethegeo-magneticallyinducedcurrents,whichaffectelectricpower-lines,andtransformers in the electric power grid, railways and any other conducting technologicalinfrastructurebelow.Alsotheconnectionofextrememagnetosphericdrivingtoinstabilitiesandirregularitiesintheupperatmospherethroughlargecurrentsandelectricfields(settinguplargeplasmaconvectionvelocities)isasofyetpoorlyunderstood.Themain reason for this poor system level understanding is that sufficiently high qualitydata from extreme SWx conditions are scarce, and despite multiple missions operatingsimultaneouslythecoverageofthevastregionsofgeospaceremainsrelativelysparse.Also-forobviousreasons–manytimesveryextremeconditionsarenotselectedforstudyduringtheinitialphaseofspacesciencemissions,sincethesecomplexresponsesarehardtofullyunderstand.Alsomost of the geo-space satellites and ground-based systemsof today arelocated at places where their data is most-useful to address and solve science questionsduringperiodsofmoderate spaceweather characterisedbymorenormalmagnetosphericdynamics.Asaconsequence,wehavehadveryfewmissionswhichhaveaddressedextremeconditions.Suchconditionsarerelativelyrare,suchthatmissionsareusuallynotdesignedtospend long-periods of mission life there. What we have observed is typically derived byfortuitous passes through such locations. One critical region, which couples the activeplasma flows in themagnetotail to the response in the nearer-Earthmagnetosphere andionosphere is at the extreme inner edge of the night-side plasma-sheet, in the transitionregionbetweendipole-likeandtail-likemagnetic fields.However,priormissionshaveonlypoorly sampled this region,with the exceptionof fortuitous transits by theNASATHEMISsatellites.There isonlyonenotableexception foramission in that location - theCombinedReleaseand Radiation Effects Satellite (CRRES)mission of NASA, as there are only few Keplerianorbits allowing spacecraft to stay in that region for extended periods of time. In order toreallyunderstandthestormtimeinneredgeoftheplasmasheetoneshouldgobacktothedatasetoftheCRRESmission.In order to define and derive future proxy measurements, i.e. essential space weatherparameters thatdescribe thephysicalanddynamical stateof theplasmasheet,onewouldalsohavetogobacktodatafrompastpolar imagingmissions likee.g.PolarandImage, inorder to relate various kindsof auroral activity toplasma-sheetprocesses,whichwenowbetterunderstand thanks to recent results fromCluster,MMSandThemis.Data from theVanAllenProbescouldalsoinformthedesignoffutureringcurrentENAimagingmissionsaswillbedescribedinChapter6(Futureoperationalfleet)inmoredetail.Besidestheneedtoextendtheground-basednetworkstolowerlatitudeswithsufficientspatialdensity,itwillbeimportant to pay special attention to the quality of measurements. Extreme events willchallenge the new instruments both in their time resolution and dynamic range.International networks arebeginning to adapt to suchnew spaceweather needs, but thefundingismostlynational,sporadicanduncoordinatedevenonaregional, letalonegloballevel.European highlights in future magnetospheric research are the recently adopted SMILEmission, and new operational modes of Cluster configurations since the spring of 2019,wheretheCluster1spacecraftactsasajust-upstreamsolarwindmonitor,whilsttheotherthreespacecraftobservethedynamicsofthemagnetosheathandmagnetopause.

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Examplesofquestions that shouldbe investigatedusingpast andpresent ground-basedandsatellitedata:

- Howdoesthemagnetospheremodulatethespatio-temporalappearanceofactivitydriven by CMEs or high-speed solar wind streams through the magnetosphere-ionospherecoupling?

- How does the impact of a single CME differ from the impact by a sequence ofseveral CMEs in the magnetosphere and ionosphere, i.e. how strong is themagnetospheric“hysteresis”effect?

- Which processes in the magnetosphere generate rapidly varying currents in theionosphere,andaretheseprocessesexternallydriven,andthenbywhichsolarwinddrivers?

- Which factors in the magnetosphere can have a significant impact on thegeomagneticstormduration,oncethesolarwinddrivingstops?

- How domagnetosonic waves, propagating across themagnetic field, couple withfield-aligned wave modes, and how does this affect the generation of magneticdisturbancesrelatedtogeomagneticallyinducedcurrentsingroundinfrastructure?

- How are plasmasheet disturbances and plasma flows coupled to the innermagnetosphere,andwhatcontrolstheefficiencyofenergyandplasmatransport?

- How do various magnetospheric waves control the plasma exchange, energytransport, coupling, and field-aligned currents, which flow between themagnetosphereandionosphere?

- Domagnetosphericprocessescauseionosphericirregularities,andifsowhichonesandhow?

IonosphereandthermosphereThe ionosphere appears at the end of the chain of SWx plasma processes. This is thetransition zone between the collisionless plasma of the magnetosphere above and thecollisionalneutralatmospherebelow.Thenameforthezonecomesfromthefactthatthereasignificantpartoftheatmosphericgas,alsoknownasthethermosphere,isionised.Spatialand temporal variability in the ionosphere are controlled by the Sun, both directly in theform of radiation and in-directly by processes in the magnetosphere as well as throughcoupling to the neutral atmosphere (thermosphere). The response of the ionosphere-thermosphere system to solar forcingvariesaccording to latitude,not justbecauseof thevariation in illumination, but also due to Earth’s magnetic field topology. A significantfractionof the quiet-time ionosphere and thermosphere variability is also drivenbywaveandmomentumsources fromthe loweratmosphere.Furthermore, it is important tonotethat the interactions between electrically charged and neutral particles in the ionospherearenotcontrolledonlybyphysics,butalsobychemistrywherecomplicatedchainreactionsareinvolved.Theabove-describedprocessescausevariations inthe ionosphericelectroncontent,whichcontrolthespatialdistributionandintensityofelectriccurrentsandradiowavepropagationconditions in the upper atmosphere.Magnetospheric processes as the primary cause forrapid current variations are described above in theMagnetospheric Section.Much of theenergy by these processes is deposited in the ionosphere through a variety of differentmechanisms,suchasJouleheatingorenergeticparticleprecipitation.Jouleheatingresultsfrom enhanced collisions between the ions and neutrals due to the imposition of electricfields moving the ions and not the neutrals. Such heating results in changes in globalthermosphericcirculation,upwellingoftheneutralgasandchangesinneutralcomposition,whichcanleadtoenhancedrecombination(theso-called“negativephase”ofanionosphericstorm)andsignificantreductionsintheelectrondensity.Particleprecipitation,ontheotherhand,enhances ionizationandcausesheatingof ionosphericelectronsbycollisionsathigh

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latitudes.Enhanced ionization impliesenhancedconductivityandthusstrongercurrents inthose regions. Significant increases in plasma density can also occur at mid-latitude, theexactcausalmechanismofwhichisanactiveareaofresearch.Thesemid-latitudeincreasesareoftenreferred toasstormenhanceddensity (SED).Theyappear tobeassociatedwithtimesof significantexpansionof thehigh-latitudeconvectionpattern intomid-latitudes inregionsofsunlightandsolarionproduction.Joule heating, auroral precipitation, and SEDs can cause strong gradients in the electrondensity and the creation of ionospheric irregularities, both of which affect radio wavepropagation. A further consequence of the atmospheric heating is that there is generalexpansionoftheatmospheretohigheraltitudes,therebyaffectingtheorbitsofspacecraftandspacedebrisbyenhancedairdrag.Asaseparatecasefrommagnetosphere-ionospherecouplingdirectimpactofsolaractivitycanappearasprecipitationofveryenergeticparticlesinthepolarcapregions.SuchprecipitationcanenhancetheionosphericelectrondensitytolevelsthatradiosignalsintheHF-regime(3-30MHz)areseverelyattenuatedoreventotallyabsorbed.Atmid-and low latitudes the impactof solarX-rayandEUVburstsonelectroncontent islargest in thedayside ionosphere.Strongburstsare likely tocausesimilarproblems in theHF communication as in the cases of polar cap absorption events. During geomagneticstormssignificantamountsofenergy fromthehigh-latitudeprocessesget redistributedtomid and low latitudes through wave activity. Such waves appear as large scale travellingionospheric disturbances that can serve as platforms for small-scale plasma irregularitiesdisturbingradiowavepropagationsimilarlyasauroralprecipitationorJouleheatingathighlatitudes.Anotherexampleofaphenomenonbuildingsteepelectrondensitygradientsandthus favouringbuild-upof irregularitiesare socalledsubauroralpolarizationstreams thatarelatitudinalnarrowstructuresassociatedwithhighplasmadriftvelocitiesandsignificantreductions in the electron density. Sharp turnings of the solar wind magnetic fieldsouthwardscancreatesituationswheretheassociatedelectricfieldpenetratespromptlytothe equatorial ionosphere and enhances the plasma drift and uplift and electric currentstheresignificantly.Consequentlystrongspatialgradientsintheelectrondensitybuildupandgeneration of plasma irregularities gets enhanced at the sunset longitudes. An additionalcomplicationof the appearanceof SWxphenomenaat lowandmid-latitudes comes fromthe variability in the shield against solar activity which the terrestrial magnetic fieldprovides.Thisshieldisattenuatedinsomelongitudinalsectorsduetotheinternalmagneticfieldtopology.ThemostwidelyknownregionofexceptionalmagneticfieldconfigurationistheSouthernAtlanticMagneticAnomalyattheeasterncoastofSouth-America,whereSWxdisturbancesappearsystematicallymorefrequentlythanelsewhereatthesamelatitudes.Due to reasons described above, characterizing the upper atmospheric conditionscomprehensively with one unified global model is challenging. Globalmagnetohydrodynamic simulations describe quite nicely large and mesoscale features(scales>100km) inmagnetosphere-ionosphere interactionsathigh-latitudes,but theyarenotapplicableatmid-and low latitudes.Ontheotherhand,globalcirculationmodelscansolve thermosphere-ionosphere interactions self consistently at sub-auroral latitudes, buttheir interactionswiththemagnetospherearetypicallydescribedwithsimplifiedempiricalmodels. Yet, in reality upper atmospheric phenomena at these two latitude regimes arecoupledwith eachother and, asmentioned above, this coupling is particularly prominentduring strong SWx storms. Furthermore, the ionosphere is oftenmodelled as an infinitelythin sheet, especially when its electrodynamic interaction with the magnetosphere isstudied.Thesheetapproximationeasilyleadstoaviewwheretheupper-atmosphereisonlyapassivemirrorofmagnetosphericdynamics.Thissimplisticviewischallengedinstudiesonextended periods of storm activity, when energy and momentum exchange between

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ionosphere and thermosphere can modify the atmospheric response to magnetosphericdriving.Ionvelocitymeasurementsasafunctionofaltitudewouldbehelpfulinquantifyingthese feedback interactions, but they are currently available only locally by incoherentscatter radars. The electric currents connecting the magnetosphere to the auroralionosphere have also been investigated for centuries with the simplification of height-integrated currents in the ionosphere. At large scales this simplification yields reasonableresults, but in the key region of substorm activity the real current system can be quitedifferent, composed of partial current closures inside the ionosphere. Comprehensiveunderstanding of regional current systems is important, because recent studies haverevealedtheircrucialroleingeneratinghighgroundinducedcurrents(GICs).Thealtituderangefrom50to400km,wheremanyinterestingmagnetosphere-ionosphere-thermospherecouplingprocessestakeplace,isdifficulttoreachwithin-situmeasurements.Traditional,long-termsatellitemissionsarenotfeasibleduetotheairdragissue,androcketor balloon campaigns can provide only sporadic data sets. Forthcoming small satellitemissions are envisaged to improve the situation, with remote sensing by ground-basedinstruments continue to play an essential role in providing homogeneous data sets tosupportmodellers.Thevalueofmagnetometernetworks,opticalmeasurementsandprobesusing radio waves either passively or actively (ionosondes and radars) is increasing withadvancements in data analysis methods. However, for big leaps forward we would needcoordinated Sun-Earth observatory systems, where models’ forecasting capabilities areimproved by systematic space and ground-based data incorporation and ensemble runs.Synergiesbetweenmeteorologicalandspaceweatherdataassimilationareenvisagedtobeusefulparticularlyforupperatmosphericmodels,wheredynamicsarestronglycontrolledbythegiveninitialconditions,similarlyasinthemodelsforlowerpartsoftheatmosphere.The advantage of observing upper-atmospheric space weather phenomena in threedimensions(3D)hasbeenacknowledgedinEurope.TheEISCATAssociationoffourEuropeanmember countrieshas started tobuildanextgeneration incoherent scatter radar system,whichwillbeabletomeasureionospherickeyparameters-includingionvelocityvectors-ina 3D volume.Also the three ESA Swarm satellites on Low-Earth-Orbits at altitudes of 450and530kmcanbeconsideredasamissiontowardsmultipointmeasurementsintheupperpartsoftheionosphere.Besidesobservingsystemsdevotedtospacescience,theEuropeanresearchcommunityharvestsdataalso fromotherglobalnetworks, theGlobalNavigationSatellite Systems (GNSS) dual-frequency receivers being the most prominent example.Observingtheionospherehasbeenabletotakeadvantageoftherapidlygrowingavailabilityof GNSS data both from ground-based networks and from space in the form of radiooccultations (RO).GNSSdata aremostlyused to generatemapsof Total ElectronContent(TEC),which are useful to show ionospheric structure and gradients, such as SEDs,whichaffectsatellitenavigation.Thesamedatacanalsobeusedtomapionosphericirregulaties,either as maps of the rate-of-change-of TEC (ROTI) or through amplitude and phasefluctuations (S4 and sigma phi, respectively). GNSS maps have also been used to detectmedium-scale ionospheric disturbances (MSTIDs from lower atmosphere forcing) and fordetecting large scale travelling ionosphericdisturbances (LSTIDs fromhigh latitudeauroraland Joule heating sources). Furthermore, GNSS receivers with high sampling rates haveappeared to be a valuable asset in the research of ionospheric irregularities, whichoccasionallycausescintillation inGNSSsignals.BesidesTECmapsmanyEuropeanresearchgroupshavedevelopedalsomethods for tomographic reconstructionsofelectrondensity,which opens ways to more comprehensive comparisons with theories and models ofionosphericproperties. Inaddition,newupgrades to theEuropeannetworkofDigisondes,haveenabledthedeterminationofthecharacteristicsoftravellingionosphericdisturbances.ThedeficiencyofGNSSandionosondenetworkscoveringonlycontinentsisgraduallygetting

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solved by space-based receivers utilizing radio-occultationmethodologies and by satellitealtimetrydata.There is now increasing awareness that during quieter geomagnetic conditions,when theSunisnotactive,spaceweatherdisturbancesarestillactive,particularlyatlowlatitude.Forinstance, ionospheric irregularities canbepresentatanytime,andcan impactgroundandspacebasedcommunicationandnavigationsystems.Theirregularitiesareinternallydriveninstabilities (e.g.,ageneralizedRayleigh-Taylorprocesses),andpredictingtheirday-to-day-variability is a challenge. There is evidence that wind and wave forcing from the loweratmospheremightberesponsibleforasignificantfractionoftheionosphericspaceweathervariability,whichisleadingtothedevelopmentofionosphericspaceweathermodelcoupledwithterrestrialweathermodel.Thewaveforcingfromtheloweratmospherealsoproducesundulations on the bottom-side F-region ionosphere, which impacts HF radio wavepropagation.Examplesofkeytopicsthatshouldbeinvestigatedusingpastandpresentground-basedandsatellitedata

- Coupling of and feedback between high, mid- and low latitude ionosphericconditionsduringSWxstorms.

- The linkage between ionospheric electron density gradients, irregularities andphase/amplitudescintillationinradiosignalsathigh,midandlowlatitudes.

- Quantitative relationship between Joule heating through enhanced ionosphericfieldsandcurrentsandatmosphericexpansiontohigheraltitudes.

- The role of waves and auroral precipitation in the closure of magnetosphericcurrentsintheauroralionosphere.

- The scale size and temporal dynamics of the ionospheric currents responsible forlargeGICs.

LithosphericimpactonregionalandlocalSWxconsequencesBeyondtheSWxrisksimposedbytheplasmaregimesingeospaceandtheheliospherethereis an additional important input and risk factor to be considered when discussinggeomagnetically induced currents, GICs. As described above themain driver for GICs, viarapid changes of magnetic field disturbances at ground level, is caused by a three-dimensionalmagnetospheric and ionospheric current system. However, the fast temporalchangesinthemagneticfield(dB/dt)causedbyrapidchangesinthatcurrentsystemdonotnecessarilycreatedangerousGICeventseverywhere.Theinducedcurrentsininfrastructurearecausedbyanelectricfieldstemmingfromtheinductionofcurrents intheground,andthus magnetic space weather events may become amplified or suppressed by the locallithospheric conductivity structure. Certain regions - of typically low lithosphericconductivity,creating largerelectric fields–maygiveriseto localorregionalproblemsforthe same kind of spaceweather thatmay have little or no impact elsewhere, in spite ofsimilar external magnetospheric SWx drivers. Thus the knowledge of lithosphericconductivities and their gradients (like e.g. along coastlines) will have to become animportantfactorintheSWxriskassessmentforindividualcountriesandregions,alongwiththegeometryoftheirinfrastructurealongsuchconductivitystructures.

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2.2. Area 2: Support to system-science approach with CoupledPhysics-basedModelling: Sun / SolarWind /Magnetosphere /Ionosphere/Atmosphere

Any scientific effort based on observations must inevitably be complemented by thedevelopment of physics based models to explain, or eventually even predict relevantobservations in each plasma regime. Predictive models are therefore critical to a robustforecastingcapability,whichprovidesworkablereactiontimestointerestsaffectedbyspaceweather. In addition, our ability to successfully predict space environment and weatherphenomenologyconstitutesameasureofthelevelofourscientificunderstanding.Traditionally, the latter has been the primary driver of solar and space physics modeldevelopment and model development has often been supported by national scienceprograms. In recentyears,however,programs likeFP7orH2020 inEuropehaveaimedorare aiming to support more specifically the development of models with capabilities toforecast space weather-relevant phenomenology and parameters. Many of the modelscreatedforspaceweatherapplicationshavebeenphenomenologicalorempirical–afocussought likely due to both limitations of financial support and limitations of physicalknowledgeandphysics-basedmodelsintheresearchfield.Whilephenomenological or empiricalmodelshavehaddemonstrable successes,we knowfrom other fields that physics-basedmodels, if possible,with assimilative capabilities, aretheultimatetoolofchoice forhigh-qualityand longer-termforecasts.Somephysics-basedmodelshavemadeitintoforecasting:Forexample,inEurope,theENLILsolarwindandCMEmodelisinuseintheUK,whereasNOAAintheUShasinrecentyearsemployedENLIL,andtheUniversityofMichiganSpaceWeatherModellingFrameworkasageospaceforecastingmodel, and theUSAF is relyingon theUtah StateUniversity assimilativemodel topredictionosphericstructureandevolution.Thesehighlypromisingdevelopmentsarearesultofrecognizingthevalueofphysics-basedforecasting.Comparedtoweather forecasting,however,spaceweathermodellingremainsin its infancy–CMEarrival time forecasting, forexample, stillhaserrorbarsofatbest12hours,andthemostcommonlyusedmodelshavestillseriousproblemstopredictmagneticfieldstrengthanddirectionat1AU.GiventheEarth’srotationrate,thismeansthatwearenotevenabletopredictatwhichtimeofthedayonagivencontinentthedisturbancewillhitEarth.Hence, there is a critical need for further development of existing models (like e.g.EUFHORIAinBelgiumorVlasiatorinFinland),aswellastheneedtodevelopphysics-basedmodelsforspaceweatherapplicationswherenoneexisttoday.Thelatterdevelopmentmaybuild on existing science modelling capabilities or involve targeted new modeldevelopments.Furthermore,alsoforspaceweatherapplicationsensembleforecasting,itiscritical to avoid reliance on single models and to increase forecast confidence. For thisreason, multiple models with the same space weather target need to be developed andmaintained.In order to foster a productive forecasting model development, a solid and continuedfunding basis is essential. Programs like H2020 can provide a valuable start-up, but thehistory of weather forecasting shows that only concentrated and long-term continuousinvestmentcancreatethecadreofexpertisenecessarytodrivedevelopmentforward.

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Cooperation and coordinationbetween thedevelopersofmodelswill be essential for thecoupling of the most relevant models all the way from the Sun to Earth to explain andpredict the entire space weather pathway for each initial solar or solar-wind drivingmechanism.Thisincludesdevelopingamechanismtoprotectintellectualpropertyrightsofmodels owners, while providing maximum space weather utility from model runs. Analternativemechanismistoprovidefundingwiththeexplicitpurposetodevelopmodelsintheopendomain,whichcan,atleastinprinciple,beutilizedbyanyinterestedparty.Complexcoupledmodelsofthekindneededtodescribemany-ifnotmost-majoraspectsofspaceweatherrequireaccesstoappropriatecomputationalresources.Thisrequirementisevenmoresignificantifmodelsaretoruninreal-timeorfasterforforecastingpurposes.Inthissituation,resourcesneedtobeavailablecontinuouslyandlie-in-waitifnotutilizedatthemoment.Computationalresourcesofthiskinddo,infact,existalloverEurope,buttheaccess requirements demanded by spaceweather forecasting constitute a significant costfactor. Development and deployment of complex models must therefore be undertakenstrategically, with a vision toward the provision of computational resources fordevelopment,andtoanevenlargerdegree,duringdeploymentforforecasting.Further, state-of-the-art researchmodels are typically not plug-and-play applications, butoften require expert knowledge to finetune the version of the operating system, theavailable libraries,aswellastheconfigurationofthemodel itself.Alsothehandlingoftheinput/outputdatacanbecumbersome,inparticularinchainedset-upswheretheoutputofone model is used as the input for the next. For all these reasons, the "Virtual SpaceWeatherModellingCentre"(VSWMC)isbeingdevelopedonbehalfofESA/SSA.VSWMCisadistributed system where models can run on remote nodes (typically the computeinfrastructureofthemodeldevelopers)butcanbestartedupandcanexchangedatawithoneanotherthroughacentralcoordinationnode.FacilitiesastheVSWMC(ortheCCMCinthe US) are essential to efficiently simulate space weather phenomena across differentphysicaldomainsasaddressedbydifferentmodels.Lastly,mostscientificmodelswill inprinciplebesufficienttosupporttheunderstandingofthe physical processes that cause extreme space weather. The use of such models fordedicated forecasts, however, requires the development of appropriate and oftenscientifically defined, metrics for improved benchmarking and model and forecastcomparisons. Measurable performance is critical for the goal of delivering actionablewarningsforusebycivilprotectionadministrationsorother interestedparties inresponsetothreatsofimpendingseverespacestorms.Findings:Today’sunderstandingof thephysicsof theSun, thesolarwindand themagnetosphere /ionosphere/atmospheresystemisincompleteanddoesnotallowthereliablepredictions,whichareneededforoperationalpurposes.Even the most advanced models at our disposal have critical shortcomings and gaps,especially incouplingtheimmensediversityoftheassociatedphysicalscales,as illustratedinthepreviousChapter1.Most present day empirical models suffer from such drawbacks, but are neverthelessimportant for immediate and cost-effective progress in Spaceweather predictionsmostlythroughparameterisation,and remainof value forverification/validationofothermodels.This translates into an urgent need for further development of advanced physics-basedmodelsandalsotocouplesuchmodelsforvariousregimesinspacewitheachother.Itwillbe essential to run suchmodels in ensemble mode as to evaluate and quantify forecastuncertainties

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Only thenwillwebeable tomakesufficiently accurate forecasts of timing, location andseverity of SWx effects in the coupled solar-terrestrial system - which are essentiallyrequiredtoprotectourtechnologicalassets.RecommendationsforArea2:

1. There should be a dedicated and sustained financial support in Europe for thedevelopment of state-of-the-art physics-basedmodels for theSun, the solarwindand the magnetospheric/ionospheric/atmospheric/solid Earth system. The fundingresponsibilitiesneedtobetransparenttoSWxresearchers,developers,andusers.

2. Scientificgroupscarryingoutsuchoverarchingmodeleffortsrequireacertaincritical

masstobeabletobothdigestscientificfindingsandimplementthoseintoadvancedmodels. We recommend to look into new funding models to support suchoverarchingmodeleffortsandcreategroupswithcriticalmass.

3. Aperiodic,e.g.,triennial,reviewofdevelopmentsuccessandrecommendationsfor

futuredevelopmentsandinvestmentsshouldbeimplemented.

4. In order to define and monitor future progress of such efforts one will need todevelop a mechanism together with space weather user groups - also using welldefined scientific and operational metrics - to verify/validate and compare theperformanceofphysics-basedmodels,boththroughoutEuropeandincollaborationwithotherglobalefforts.

5. Using theNASACommunityCoordinatedModellingCentre, CCMC,asa rolemodel

foratest-bedofcoupledpredictivemodels, coordinatedEuropeanefforts (likee.g.theVirtual SWxModelling Centre, VSWMC) should be supported to combine andcouplestate-of-the-artmodelsintoanoperationalchainofpredictivemodelsfromtheSuntoEarth.

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2.3. Area 3: Consolidation of National, Regional and European RiskAssessments

Space weather risks constitute an ever-evolving landscape. The successful mitigation ofthese risks requiresadetailedandcontinuingassessmentofSWx impactpathways,of therisksthatflowfromthesepathways,andoftheoptionstomitigatetheserisks.Onlywhenmitigationoptionsareknownisitpossible

a) to assess the socio-economic value of taking action (i.e., does mitigation costsignificantlylessthantheeconomicloss),andthus

b) toestablishrequirementsformitigationincludingbothsystemhardeningandspaceweatherforecasting.

Spaceweatherrisksarecontinuouslyevolvingwiththeadvanceofscienceandtechnology.Thisisshownbytheevolutionofspaceweatherimpactsontechnologicalsystemssincethefirstrecordedimpactsonelectrictelegraphsystems[7],thenthroughimpactsontelephones[51],radiocommunication[37]powergrids[41,50],andrailways[34].Inrecentdecadestherangeofimpactshasexpandedgreatlyasourmodernworldhasmademoreandmoreuseoftechnologiesineverydaylife.Thisishighlightedtodaybyourcriticaldependence on electric power (whose supply is an area of major cooperation betweenEuropeannations) andon real-timecommunications (bothvoiceand internet). Looking tothenearfuture,satellitelocationandtimingservicesarenowacriticalelementineverydaylife,asrecognisedinEuropebythedevelopmentoftheGalileoGNSSsystem.Thesesatelliteservices often underpin other key technologies such as mobile communications,autonomous vehicles and financial services. Other new dependencies emerge from thediscussion of the new catch-phrase “internet of things”. While stock markets have nowfoundawork-aroundforGNSStime-stamperrorscausedbySWx[3],theremaybeahiddenGNSSriskwhenotheractorscoupletheirindependentlyfunctioningsystemstogether.Manyactorsmay not be aware ofwhere their systems embedGNSS timing devices, and hencethat coordinated actions via internet can fail if SWx corrupts the timestamps provided bythosedevices.AnimportantexampleistheconcernformaritimesafetyauthoritiesthatlossofGNSS signals candisrupt the flowof accurate sensordata into systemsused to controlships[12].Thus the risks posed by spaceweather should be regularly re-assessed to identify wherechangesintechnologyhavealteredthepotentialimpactofspaceweather,anactivityinlinewith wider risk management practice followed by governments across Europe (e.g. seeOECD Toolkit for Risk Governance, http://tinyurl.com/y3uh92h3). The promotion andsharingof that goodpracticewithin Europe is also a keyobjectiveof the EU’sUnionCivilProtectionMechanism[19](http://data.europa.eu/eli/dec/2013/1313/oj).This Mechanism requires member states to develop risk assessments of natural andtechnological hazards, and to share non-sensitive information from those assessments.Thus, there is nowa European framework for national and regional risk assessments thatwill encompass spaceweather alongside other societally-important hazards, e.g. as in therecent assessment of the space weather risk to the Italian power grid [57]. It is alsoimportant for Europe to share good practice on space weather risk assessment withcountriesinotherpartsoftheworld,mostobviouslythesubstantialprogrammeofUSworkthat is progressing under the auspices of the Space Weather Operations Research andMitigation Subcommittee (www.sworm.gov). This programme is drawing in advice fromEuropean experts and hence provides a good example of international coordination. For

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otherUSconsiderationsonSpaceWeatherrisksandmitigationneedsseearecentreportbyKnippandGannoninJ.ofSpaceWeather2019,andreferencestherein.3IntegratingspaceweatherknowledgeintoriskassessmentandmitigationWepresenthereascheme(Figure1)thatwillhelpriskmanagers(whetheringovernmentorindustry) to appreciate this chain and thus enable effective assessment of spaceweatherrisks and theirmitigation.We start at the upper left of Figure 1wherewe highlight thatspace weather is a persistent feature of the environments within which human activitiestakeplace.TheEarthhasbeenexposedtospaceweathersincelongbeforehumansevolvedon the surface of our planet. But, spaceweather has become significant only aswe havedevelopedtechnologiesthataresensitivetospaceweather,asnotedabove,andasairandspacetravelhavebroughthumanstoregions(theatmosphereabove10km,andspace)thataremoreexposedtospaceweather.

Figure 1. Risk-to-requirements chain for spaceweather impacts on critical infrastructures.The evolutionof technology, andof scientific and engineering knowledge, requires regularreviewsoftherisksposedbyspaceweatherandofrequirementsformitigationofthoserisks.

It is the interaction of space weather with technologies, particularly those embedded incriticalinfrastructures,thatleadstoadverseimpactsasweshowinFigure1.Theseimpactsevolve because technological innovation enables us to improve the performance of thoseinfrastructures. Modern infrastructures have greatly improved the quality of life forEuropean citizens, and for other people around the world, including those in developingcountries(e.g.withthehugegrowthinuseofmobilecommunicationsacrossAfrica).But,as3Knipp,D.J.,&Gannon,J.L.(2019).The2019NationalSpaceWeatherStrategyandActionPlanandBeyond.SpaceWeather,17.Doi:10.1029/2019SW002254

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asideeffect,theyhavemademodernsocietiesvulnerabletotheimpactsofspaceweather.Thus it is vital to assess the risks that arise from these impacts, and to mitigate anysignificant risks. Scientific and engineering knowledge is crucial to this process. It gives usinsightintowhatareareasonableworst-casespaceweatherconditionstobeconsideredbygovernments and industry when assessing risks. In line with risk assessment for othernaturalhazards (e.g. riverandcoastal flooding,extremesof temperature, volcaniceffects,…), the reasonable worst-case is taken as an event that may occur once in one to twohundredyears.TheCarringtoneventof1859iswidelyconsideredtobeagoodexampleofsuchanevent,andhencehasbeenwidelystudiedsoastoimproveourunderstandingofthereasonableworstcase.Someriskassessmentswillconsidermoreextremecasesthatoccuron longer time scales, if the potential impacts of those cases are catastrophic. For spaceweather, the prime example is the potential impact on nuclear infrastructures, such asreactorcontrolsystems,whereitisstandardpracticetoconsiderrisksthatmayoccuroncein10000years[30],andhencewemustconsiderthepotentialofextremeradiationstorms,todisruptelectroniccontrolsystemsonthesurfaceoftheEarth.Notealso thatscientificandengineeringknowledge isalwaysevolvingandthat thisdriveschanges in our understandingof spaceweather risks.Anotable recent examplehas beenthescalingupoftherisksthatspaceweatherposestopowergrids.AtthebeginningofthiscenturythatriskwassetbyexperiencegainedduringthegreatgeomagneticstormofMarch1989, which led to a large-scale power blackout in Quebec [10, 25], and to transformerdamageintheUK[55]andtheUS[59].Butmoredetailedassessmentusingawiderrangeofhistoricaldatashowedthattheriskneededtobescaledupbyanorderofmagnitude[11,27].This evolution of knowledge adds greatly to the challenges that space weather poses tomodern technologically-based societies. When combined with the pace of technologicalinnovation, it creates a rapidly changing landscape for space weather risk assessments.Whilstthisfitswellwiththemodernconceptofregularriskreviews,itcansometimesbeachallengetoengageoperatorsofsystemsatrisk,whowillnaturallyprioritisefrequentriskswithwhichtheyarefamiliar.Thishighlightstheimportanceofscienceinunderstandingrareandextremeriskssuchasseverespaceweather,andalsotheresponsibilityofscientiststocommunicatethatknowledgetooperators.There is alsoa growingbodyofevidence thateveryday fluctuations in spaceweather canimpacttechnological infrastructures.ForexamplestudiesofUSinsuranceclaimsrelatedtoelectricalproblemsshowamarkedcorrelationwithspaceweatherconditions [54].Similarcorrelationshavebeenreportedinstudiesontheperformanceofelectricitymarketsaroundtheworld,includingEurope20,21,22].Everydayspaceweatherisalsoasignificantfactorinother sectors of the economy including precise positioning services (e.g. as shown in arecentsocio-economicstudyundertakenforESAbyPriceWaterHouseCoopers,footnoteonpage 9). None of these effects are catastrophic but all suggest that infrastructureperformancemay be improved by taking account of spaceweather.However, experiencesuggeststhatoperatorscanbereluctanttoengagepubliclywiththisissueduetoconcernsabout reputational impact (and perhaps also as an understandable reaction to spaceweatherbeingwidelyusedincontemporaryfictionasabasisforscarestories:storiesthatcanbeveryentertainingbutgofarbeyondwhatsciencecanjustify).Thusthereisaneedtoencourage realistic public discussion of everyday space weather, so that operators canbenefitfrom(ratherthanfear)engagementwithpublicdiscussionofthetopic.Thestructureofknowledgeshown inFigure1canprovideaway todo this–highlightinghowscientificandengineeringknowledgecanhelpoperatorstoassessspaceweatherrisks,whilstshowinghowtheserisksareanaturalresultoftechnologicaladvances.Thisisalreadyhappeningassome sectors (notably satellite operations) develop better links with the space weathercommunity.

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Scientificandengineeringknowledgeisalsocentraltothemitigationofspaceweatherrisks.Can we use that knowledge to eliminate those risks by better engineering of vulnerablesystems? Or do we need to adjust the operation of those systems when adverse spaceweather occurs? The former will always be the first choice if it can be done in a cost-effectivemanner:agoodcontemporaryexampleisthemigrationofstockmarketstowardsuse of high-precision ground-based timing services [3], thereby eliminating the risk thatspaceweatherwill disrupt GNSS timing services. However, there are important exampleswhere it is not cost-effective to engineer out impacts, e.g. the electric transmission grid,where the risk of disruption arises from geomagnetically induced currents (GICs), whichenter the grid as a side effect of the electrical grounding that is fundamental to the safeoperation of all electrical systems. Thus grid operators will adjust the operation of theirsystems to copewith adverse spaceweather conditions, just as they adjust to copewithotherriskfactors(notablynormalweather).Theywillalsoinvestinsomehardeningofgridsystems,butoperationaladjustmentsareakeyelementinthemitigationofrisks.Buttheycanonlymakethoseadjustmentsiftheyhavegoodforecastsandnowcastsofadversespaceweather,aswellaspriorsimulationstohelpthemplanforsevereevents.Scientific and engineering knowledge is essential to promote a thoughtful approach tomitigationofall spaceweatherrisks,onethatgoestotherootof theproblemscausedbyspaceweatherandthatdoesnotfocusononeaspecttothedetrimentofotheraspects.Aclassicexampleisthemitigationofsatellitechargingwherethereareseveralprocessesthatcan cause problems, some that can be substantially mitigated by good engineering andsome that require operational measures backed by forecasts. Experience shows that,withoutgoodknowledge,thespectrumofchargingproblemscanbeover-simplifiedtofocusonlyonaspectsthatcanbemitigatedbyengineering.Thebottomlineisknowledgematters,togetherwithgoodhumanjudgementonhowtousethatknowledge.The final step in thechain shown inFigure1 is requirements, the requirements for futureobservations and models to help us respond to space weather. We will discuss these indepth in the next section. Herewe just note that these requirementsmust flow from anunderstandingofspaceweatherrisksandtheoptionsavailabletomitigatethoserisks.CustomisingspaceweatherriskstoEuropeThe structure shown in Figure 1 is well-suited to the European landscape since it can beapplied at national, regional andEuropean levels – and indeedat a global level to enablewiderexchangeofideasandpoolingofresources(mostlyobviouslytodevelopspace-basedmonitoring of space weather conditions). It is a firm basis for increased governmentunderstandingoftherisksandaswellastheengagementofnationalcritical infrastructureprotection andother administrations. Increasedunderstandingof spaceweather risks hasalready resulted in the development of an appropriate national response to the spaceweatherthreatinsomeEuropeancountries:

- Netherlands(seehttp://tinyurl.com/yxnvfe3r)- Sweden(seehttps://www.msb.se/en/Prevention/Space-weather/)- UK(seehttp://tinyurl.com/oqbpeoe)- Finland(seehttp://tinyurl.com/y55mtm9l))

In Austria, Belgium, Italy and Norway similar assessments are under way. At a widerEuropeanleveltheEUJointResearchCentresupportedanumberofworkshopsandreportsbetween2011and2016,workingwithpartnersinnationaladministrationsandwiththeUS,e.g.33,.34].TheseJRCactionshavebeencomplementedby inclusionofspaceweather inother European risk management fora, e.g. multi-national meetings of civil protectionofficersandinsuranceexperts.

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It isverytimelyto increasethepaceofthiswork-encouragingspaceweather impactandrisk studies that recognise regional differences across Europe, whilst recognising that theinterconnectednessof twenty-first century infrastructurescanmagnify regional impacts tocreate large-scale spaceweather risksacrossEurope.Forexample,major radiationstormscan force airlines to avoid trans-polar routes and divert to lower latitudes. For sometranspolar routes, e.g. Dubai-Los Angeles, these diversions may bring extra traffic intoEuropeanairspace.ThisincreasedpaceneedsactionatbothnationalandEuropeanlevels.TheEUiswell-placedtoencouragebothlevelsofactionviaacontinuationoftheexcellentworkpreviouslydoneatJRC,inparticularbypromotingperiodicreviewsofevolvingspaceweatherrisksacrossthefull range of critical infrastructure sectors (e.g. energy, transport, finance, …). Given itscontacts with civil protection authorities across Europe, a JRC activity can stimulate andencourage national assessments of space weather risks across Europe. The JRC canencourage good practice, in particular the need for sector-led risk analyses. Once theimpactson individual infrastructuresectorsareunderstood,wecanunderstandwherearethecommonelementsthatwarrantactionataEuropeanlevel.Acriticalcommonelementistheidentificationofspaceweatherphenomenathatdriveimpactsindifferentsectors,andthequantificationoftheprobabilitythatthosephenomenawillreachdisruptivelevels.Thisshould recognise that themost extreme events can drive an equator-ward shift of spaceweather impacts, such that effects common in the Arctic can reach the Mediterraneanregion.But itshouldalsorecognisethatmoderatespaceweathercanalsohavesignificantcumulative impacts –contributing to wear and tear on vulnerable systems, and to minordisruptionsthatarepoorlyunderstood.MappingspaceweathertofutureactionsItiscriticaltodeterminewhichactionstoreducespaceweatherrisksareworthwhileataneconomiclevel.Thustheassessmentofrisksmustbecomplementedbystudiesofthesocio-economicimpact–inparticular,studiesthatassesshowmitigationcanreducetheeconomicimpactofadversespaceweather,e.g.as inrecentpapers[15,46]thatexplorehowfuturespace weather missions to the Lagrange L1 and L5 points can maintain and enhanceforecasting capabilities. These studies also show that a key element in socio-economicimpact is thetimerequiredtorecover followingaspaceweatherevent.Betterknowledgeenablesfasterrecoveryandhencereducedeconomicimpact.AgoodexamplewecanlearnfromisthedisruptionofairtrafficcontrolbyasolarradioburstinNovember2015[38];thisclosedairspaceoversouthernSwedenforseveralhoursleadingtoflightdelaysinSwedenandmanyothercountries.Betterawarenessofcurrentspaceweatherconditionsandtheirpotential impact could have shortened the period of disruption to minutes rather thanhours.Whenturning ideas into futureactions,wemustrecognisethat themanagementofspaceweather requirements canbe challenging. In particular, it is important to strike a balancebetween the natural evolution of requirements and the setting of clear goals for specificprojects.Clearandstablerequirementsarethefoundationofsuccessforanyproject.Thus,asshowninthelowerrightofFigure2,itiscriticaltotakeasnapshotoftherelevantprojectrequirementsat the startof theproject.Once set, changes to theseproject requirementsshouldbeallowedonlyafterverycarefulthought.Findings:AtpresentwelackacompleteandtrueevaluationanddescriptionofEuropeanSWxrisksformost individual countries and particularly for regional and over-regional risks, which are

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emerging from the increasing interdependencies and interconnections of the potentiallyaffectedinfrastructure.The risks emerging from SWx events - and thus the definition of user-requirements -willobviouslynotbethesamefordifferentpartsofEuropeor forEuropeanactivities inotherpartsoftheworldorinspace.Anysuchrisksarealsodifferentforspaceandground-basedtechnologicalassets.There is an urgent need for a coordinated European assessment of national and regionalrisksandconsequentpotentialsocio-economicimpactsofavarietyofspaceweatherevents,bothforextremeandaveragedailysolaractivity.OnlyonthebasisofsuchariskassessmentafullcatalogueofEuropeanUserRequirementscanbecompiledforthedevelopmentofafutureEuropeanspaceweatherservicefunction.RecommendationsforArea3:

1. Encourageandenablemember-statestocarryoutacoordinatedEurope-wideeffortof national risk and socio-economic impact studies of SWx events – in closecollaboration between SWx scientists and engineers working with potentiallyaffectedinfrastructure.

2. Supportthecombinationandexpansionofnationalriskassessmentsintoregional

and Europe-wide risk and impact analyses, addressing the interdependency andconnectivityofmany - if notall - technological infrastructures inEurope -buildonlaudableeffortsalreadyconductedbytheEC-/JRCand in linewiththeECmandateforcoordinationofsuchriskassessments(asprovidedbytheUnionCivilProtectionMechanism).We strongly recommend that spaceweather be included in the nextiterationoftheriskstobeaddressedbyJRC.

3. Support and enable awareness about and the dissemination of such risk

assessments tonationaldecisionmakers,butalsotothecommunitiesofscientists,serviceprovidersandend-usersalike.

4. Createanactiveexchangeforumfortri-lateraldiscussionsandregularlyupdated

information exchange between SWx -Scientists, End-Users and Service Providers.Theannual“EuropeanSpaceWeatherWeek”,ESWW,servesasagoodmodel.

2.4. Area4:ConsolidationofEuropeanUserRequirementsESAcarriedoutextensivestudiesofspaceweatherservicerequirementsinthefirstdecadeofthiscentury.Twoparallelstudiesin2000/2001[12,43]providedcomprehensiveanalyses,whilst a later study looked at requirements that could be addressed on cubesats [26]. Allthese studies were consolidated during the first period of the ESA Space SituationalAwarenessprogramme,producing the requirementsdocuments [16,17,18]onwhichESAhasbuilt thespaceweatherelementof itsSSAprogramme. Informaldiscussions,withESAandacross thewidercommunity,havenotedtheneed forcontinuedelaborationofspaceweather requirements to reflect subsequent changes in space weather risks, and in ourunderstandingof those risks. Such improvementmust provide a clear and comprehensiveprioritisationof requirements, addressing the spreadof spaceweather risks across criticalEuropean infrastructures on the ground aswell as in space, and engagingwith the spaceweather risks identified by civil protection authorities across Europe. This is a challengingtaskas itrequiresaprocess(andsufficientresources)toengagewiththespecificneedsofindividual European countries and then to consolidate those into a coordinated andprioritisedprogramme.ThescaleofthetaskhasbeendemonstratedbyESA,throughtheir

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fundingofa2016studyofrequirementsforonecountry(theUK).Thisstudycouldprovideinsightsforawiderrequirementsstudyacrossallcountries,perhapsundertheauspicesoftheEU’sCivilProtectionMechanism[19].Intherestofthissection,wediscussanumberofkeyinfrastructures(power,GNSS,aviationandsatellites),andoutlinehownationalandregionalgoalsforspaceweathermitigationwillinevitably be diverse due to natural variations in the level of space weather risk acrossEuropeassummarisedinTable1below.WenotewheretherearerecentscientificstudiesthatcanguidethosegoalsandalsohighlightwheretherearealreadybroaderEuropeanandinternational programmes that can feed valuable insights to European requirements formitigationofspaceweatherrisks.The risks to the power grid are receiving increasing attention across Europe with recentpeer-reviewedassessmentscoveringAustria/centralEurope[4,5], [60], thewhole islandofIreland[8,9],Sweden[58],Italy[57]andSpain[56].Otherrecentstudiescomparedimpactsonpowergrids inFranceandon themain islandof theUK [32,33], andusedpartsof theRussianpowergridasatestcasefordevelopmentofhigh-levelriskassessmenttools[55].Theseassessmentsshowthat therearesignificant risks topowergridsacrossEurope,andthat requirements for mitigation must take account of key factors that vary betweencountries: (a) the roles of substorms, sudden commencements and the ring current indrivinggeomagneticvariations;(b)variationsingroundconductivity;and(c)thetopologyofthe power grid. As some of the risk may be different for different parts of a particularinfrastructuredue to local geometry and relative location to local conductivity conditions,userrequirementspriorriskassessmentmusttake intoaccount localscenarios for intensegeomagneticvariationsandlocalconditionssuchasgroundconductivityandgridtopology.For operational mitigation, requirements for nowcasts/forecasts must address localgeomagneticvariations,aswellasforecastsofupstreamdriversofthosevariations,e.g.thesolarwind.Another important spaceweather impact is the disruption of GNSS services due to rapidchanges in TEC and to ionospheric scintillation. The TEC problem has substantially beenaddressedbytheEU/ESAinvestmentinEGNOS[24].Thisprovidesnear-real-time(seconds)corrections to suitably equipped GNSS receivers such that GNSS-derived positions areaccurate to 10 to 20 metres across most of Europe (south of 63° latitude). This is, forexample, sufficient to ensure safe use of GNSS for aircraft navigation. In extreme spaceweather conditionswhereEGNOScannotprovideadequateaccuracy, itwillwarnusers toswitch to alternative navigation systems. In such conditions, ionospheric scintillationmayalso become significant, degrading the quality of GNSS signals reaching the ground andpotentially leadingto lossofsignal.Thustherequirements formitigationofGNSS,beyonduse of EGNOS, should focus on the need to forecast space weather conditions that candisruptuseofEGNOS,sothatuserscanplanaheadforthatdisruption.Theseforecastsmustidentify which countries and regions will be impacted. There are also requirements toimproveEGNOSaccuracy:northof63°latitude,andonthebordersofEurope,e.g.extendinggoodaccuracyintoAfrica.Space weather has a wide range of impacts on aviation, as shown in Figure 2 below.Radiationeffectsonavionicshavethepotentialtodisruptcontrolsystemsonmodern“fly-by-wire”aircraft[13];solarradiobursts[39]andionosphericeffects[2]candisruptaircraftnavigationandflightcontrolsystems,whilstionosphericeffectscandisruptcommunicationswithairtrafficcontrol(e.g.theSeptember2017lossofcommunicationswithanAirFranceflight [51]).There isalsoarisk, inverysevereevents, that radiationexposureofcrewandpassengersmayrequiremitigatingaction[39].Therearerequirementstomitigatealltheserisksbyprovidingpre-flightforecastssothatairlinescanfactortheserisksintotheplanning

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of specific flights (perhaps changing routes or even grounding planes in extremecircumstances)andsothatpilotscanbereadytorespondifproblemsdooccurin-flight.Inrecent years, the International Civil Aviation Organisation (ICAO) has been developingprocedurestoprovidethesebriefings.ThusEuropeanrequirementsshouldbealignedwiththewiderinternationalrequirementsestablishedbyICAO.

Figure 2. The “pilot’smantra” of Aviate, Navigate and Communicate captures the priorityorderoftasksneededtoflysafely.Allthreetasksareatriskfromadversespaceweather.

Satellites are another critical infrastructure vulnerable to space weather. Fortunatelysatellite builders and operators, in Europe and around the world, have decades ofexperienceofspaceweather.Builderscanincorporateahighdegreeofresilienceintotheirsatellites,andoperationsteamsareskilledat investigatingandresolvinganomaliescausedbyspaceweather.Nonethelesstherearestillmajorrequirementsforbettercharacterisationoftheworst-casespaceweatherfacedbysatellites,sothatbuilderscanrefineandextendtheirdesignstandards,e.g.toaddressinnovativeoperationssuchaselectricorbitraisingforgeosynchronous satellites. In addition, operations teams have continuing majorrequirementsforforecasts,nowcasts,andpost-eventanalysisofadversespaceweather,sothattheycanplanfor,respondto,andanalysesatellitedisruption.Keyrequirementsareforinformationonchargedparticleenvironments,inallEarthorbitsandininterplanetaryspace(these particles affect satellites by surface and internal charging, single event effects inelectronicdevices,andradiationdamagetosolararraysandothersatellitesystems).Theserequirements extend to human exploration, especially if we extend exploration to otherbodies such as theMoonand laterMars. There are also requirements for informationonspace-weather-driven changes in atmospheric drag for satellites in low earth orbit (dragaffectstheschedulingofsatelliteoperations,plusthemanagementofcollisionrisksandre-entry). ESA is an important end-user by itself for such requirements in respect of its ownsatellite operations, as are other EU-linked bodies that operate satellite systems such asGalileoandCopernicus.TherearealsomanypublicandprivatesectorusersacrossEurope,reflecting thewideuseof satellite systemsandapplicationsbygovernmentsand industry.However,thereisnoobviousdifferentiationofrequirementsbyregionswithEurope,ratherthereisdifferentiationbysatelliteorbit.

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TableX.Examplesofspaceweatherriskstocriticalinfrastructures:regionalissuesandhigh-levelrequirements

Infrastructureatrisk

PrimaryRisk Regionalissues High-levelrequirements

Powergrid Geomagneticallyinducedcurrents(GIC)leadingtovoltagecollapseandpoweroutagesofmanyhourstoafewdays.Insomecases,thismayleadtodamagetogridsystemssuchastransformers.

RiskisgreatestinnorthernEuropeduetosubstormeffects.ButalsosignificantriskinMediterraneanareaduetosuddencommencementsandringcurrenteffects.

*ModellingofgeoelectricfieldsandconsequentGICinpowergrids*ForecastingtraveltoEarthofheliospherictransients(CMEsandSIRs)*Modelling/forecastingmagnetosphericresponsetoheliospherictransients

Aviation Enhancedatmosphericradiationleadingtodisruptionofavionicsystems.Alsoincreasedradiationexposureforaircrewandpassengers.

Radiationfluxincreaseswithlatitude,sogreatestonroutesthatgonorth,e.g.EuropetoWestCoastofNorthAmerica,irrespectiveofcountryoforigininEurope.

*ForecastsofSEPevents(forpre-flightbriefings)*Real-timeinformationonSEPevents(forin-flight-management)*Post-eventinformationonradiationfluxesandfluences(toassesshumanexposureandforanomalyanalysis)

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Aviation LossofGNSSpositionduetorapidchangesinTECand/orionosphericscintillation.

Scintillationeffectsaregreaterinpolarandequatorialroutes.Soeffectsaregreatest(a)onlong-haulroutesovertheseregions,irrespectiveofcountryoforigin,and(b)onshort-haulroutesinfarNorthofEurope.

*ForecastsofdisturbedTEClevelsandofionosphericscintillation

Aviation LossofHFcommunicationsduetoD-regionabsorption(SEPevents,largeflares,relativisticelectronprecipitation(REP))

SEPeffectsaregenerallylimitedtopolarregions.Flareeffectsaregreateratlowerlatitudesbutlimitedtodaytime.REPeventsarerarebutwillaffectmid-latitudes.

*ForecastsofhighSEPfluxes*Forecastsoflargeflares

Logistics LossofGNSSnavigationduetorapidchangesinTECand/orionosphericscintillation.

Scintillationeffectsincreasewithlatitude,soriskisgreatestinnorthernEurope.

*ForecastsofdisturbedTEClevelsandofionosphericscintillation

Emergencyservices

LossofGNSSnavigationduetorapidchangesinTECand/orionosphericscintillation.

Scintillationeffectsincreasewithlatitude,soriskisgreatestinnorthernEurope.

*ForecastsofdisturbedTEClevelsandofionosphericscintillation

Satellites Enhancedspaceradiationleadingtodisruptionofsatellitesystems.

Riskvarieswiththesatelliteorbit,e.g.GEOmoreexposedthanLEO.Butmost,ifnotall,countrieshaveinterestinmostoperationalorbits

*ForecastsofhighSEPfluxesthatcancausesingleeventeffects*NowcastofthespectrumofSPE(hardness)afteronset

Satellites Enhancedsatellitechargingleadingtodisruptionofsatellitesystems.

Riskvarieswiththesatelliteorbit,e.g.GEOmoreexposedthanLEO.Butmost,ifnotall,countrieshaveinterestinmostoperationalorbits

*Forecastsofhighfluencesofenergeticelectrons,especiallyMeVelectronsthatcauseinternalcharging,butalsokeVelectronthatcancausesurfacecharging

Insummary,thereisaneedforanimprovedsetofEuropeanspaceweatherrequirementsthat address the risks that space weather poses to critical infrastructures and othervulnerablesectorsacrossEurope,andthatengageswithspaceweatherresiliencegoalssetatnationalandregional levels.Theserequirementsshouldconsolidate individualneedssoas to identify where those needs are best served at a European level, as in the fourinfrastructure examples discussed above, but also considering other major Europeaninfrastructures includinggas, rail and roadnetworks, telecommunications, foodandwatersupplies, finance, and emergency services. These consolidated requirements should beinformedbypreviousworkbyESA,andbyotherplayersacrossEurope.Elaborationof the

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requirementswouldbenefitgreatlyfromafreshanalysisbasedonstudyofspaceweatherimpactsoncriticalinfrastructuresandoftheprioritiesthatflowfromthosestudies.Findings:Atpresentwe require results fromthe fullEuropean-wide riskassessmentasdescribed insection3toelaborateandcomplementthecustomerrequirementscompiledbytheESASSAprogramme [16,17,18]. ESA SSA requirements have been the baseline that was used todevelop the current network of SWx Expert Centres and ExpertGroups, but a continuouselaboration of the requirements will be needed to take into account the continuouslyevolvinguserlandscapeandscientificknowledgebase.Continuous elaboration of the understanding of the user needs for tailored servicesprovidingactionableinformationismandatoryandatthemomentthisiscarriedoutonlyintheframeworkoftheESASSAProgrammewithlimitedresources.OnlyonthebasisofafullEurope-wideriskassessmentasdescribedinsection3cananewandcompletecatalogueofEuropeanUserRequirementsbecompiled,addressingrisksonallassets.InthiscontextwenotethattheEuropeanspaceassetscompriseonlyabout10%ofallassetsatriskfromSWx.Itisalsocriticalthatthiscompilationisupdatedtypicallyevery5years.Thecatalogueofuserrequirementsshouldbea“livingdocument”withupdateintervalsofe.g.every5years,sincetheinfrastructuresandtheirparticularvulnerabilitiesandresilienciesconstantlychangeanddevelop-asdoesthescientificunderstandingofpotentialSWxeventsandtheirassociatedrisks.RecommendationsinArea4:

1. Support and enable a coordinated European wide effort to elaborate EuropeanSWxuser requirementsbasedonneedsasspecifiedby localregion(suchasarctic,sub-auroral, mediterranean) and infrastructure domain (communication, energy,health, finance, etc.), addressing the risks from SWx impacts on space-based andground-based infrastructure - build on efforts already conducted by the ESA SWEProgramme1and theEC/JRC for Infrastructure -and re-establishSWxasa task fortheJRCactivities.

2. Therewillbeaneedtoprioritiseuserrequirements inthecatalogue,basedasfar

aspossibleontheirvalueinmitigatingparticularimpacts,e.g.specificallyforecastshelpingoperatorstomaintainpowersupplies,navigationorcommunication.

3. Enhancetheexchangeandupdatingofinformationaboutuserrequirementsintri-

lateral discussions between SWx -Scientists, End-Users and Service Providers. Formost requirements the description of context and clear rationale for the expectedimpactwillbecrucialtodeterminetheneededforecasttypeandquality.

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2.5. Area 5: “R2O” and “O2R” or how can SWx scientists interfacewith candidate organisations for SWx services – in Europe andglobally

Unlike terrestrial weather, which is a mature science, space weather is in its scientificinfancy. The immature nature of the field, the complexity of data sets, and the rapidlyevolving character of models make the close involvement of active researchers highlybeneficial tospaceweatherservices.Practisingscientistscandistinguishadataglitchfromvaliddata, andvalidmodeloutput fromerroneous results. Furthermore,ourdata sourcesare sparse and often ephemeral, a situation which mandates that we use any availableinformation to form the best possible picture of space weather and to produce the bestpossible forecasts.We thusneeda flexibleapproach,whereevery institutionand countrycanparticipatetothebestoftheirabilities,andwhichcombinesscientificandinterpretativeskillsatmanyinstitutions.Suchaninclusivemodelalsoprovidesrapidutilizationofemergingcapabilitiesandknowledge.Finally,itsupportsdecision-makingbasedonknowledgeofwhatispossibletodayandwhatisemergingintheresearchcommunity.Despiteaveryrestrictivebudgetarysituation,ESA’sSSASpaceWeatherSegmenthasbeenhighlysuccessfulinintegratingawiderangeofspaceweatherservicesacrossEurope,andindevelopingaCoordinatedCommunicationProtocol(CCP)forconsistentEuropeanmessagingduringspaceweatherevents.This success isa resultof theunderlying inclusiveapproach:while relying on a centralised management and coordination, ESA’s approach isdecentralised and organised in the form of Expert Groups, creating a network of ExpertService Centres (ESCs). These ESCs integrate diverse scientific and analytic experience atmanyinstitutionsandmanycountries.Hence,theyformatotal,whichismuchlargerthananysingleinstitutioncancreate.Scientistswhogeneratetheknowledgeandthemodelsaredirectlyinvolvedinthetransitioningofthisinformationintooperations,andtosomeextenteven in theoperations themselves. ESA’sprogramme is also, toa largedegree, guidedbythese scientific experts, and is therefore set up to evolve in the best possibleway.Whileuser helpdesk and system monitoring functions are provided by a service coordinationcentre,ESA’sSWxESCscan,infact,provideregionalservicesandcommunicatedirectlywithusers,ensuringthatusersareawareofwhat ispossiblenowandwhat isemergingasnewcapabilities,andthatprovidersunderstanduserneeds.4However,ESA’sSSAprogrammecouldbeimprovedevenfurther.Firstofall,theprogrammehasbenefittedtoalargedegreefromscientificresearchanddevelopmentlargelyfundedbynational sources, by the European Union, or by ESA’s science programme.We note thatfurther progress in space weather capabilities requires dedicated research anddevelopment, which is unlikely to happen without a dedicated funding source. Thiscontinuoussupportdoesnotexistto-date,andfundingavailablefortheexistingprogrammeremains severely limited. In addition, the programme should re-orientate itself toward anincreased emphasis on development and production and a de-emphasis of overheadactivities.In conclusion, the ESA SSA approach toward decentralization, networking and inclusion,proximitybetweenscientificresearch,transitiontooperation, isconsideredtobethebestpossiblemodeltoyield immediatesocietalbenefitswhilesimultaneouslyallowingthefieldto mature in parallel. It should be the model for a European space weather service. For

4ESASSAhascarriedoutastudyonArcticSWxUserRequirements in2016and is startingstudiesonMediterraneanUserRequirementsin2019.

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further progress, it is also essential that funding sources be created,which support spaceweather-focusedresearchanddevelopmentinasustainedfashion.WefurtheradvocateforR2OcoordinationbetweentheESAprogramme,andnationalactivitiesinsideEuropeaswellasEUprogrammes.Finally,EuropeanSpaceWeatherservicesshouldbecontributingto,andbenefitingfrom,relatedSpaceWeatheractivitiesworld-wide.Findings:ThereisnodoubtthatinitialSWxservicesandpredictionsofeventsandeffectsareurgentlyneededtodaybyavarietyofendusersanddecisionmakerstoprotecttheirassetsinspaceandontheground–butthepresentSWxknowledgebaseisinsufficientforthistask.The development of future improved SWx services must be driven by specific UserRequirements(seeChapter4),andmustbebased-andconstantlyimproved-onthebasisofathoroughSWxRiskAssessment(seeChapter3).Futureservicesshouldcontinuouslybeimprovedonthebasisofthebestavailablescientificknowledge – includingmaking use of the best performing, coupled and “state-of-the-art”modelsavailable.ApromisingapproachtodeveloptherequiredfutureEuropeanspaceweatheractivitiesandservices can best be described as an iterative loop betweenR2O andO2R inwhich thereshouldexistacontinuousiterationandfeedbackbetween:a)newimprovedscienceunderstandingandsupportingobservations,b)evolvingrequirementsofEuropeanend-usersandinfrastructureproviders,andc)improvedpotentialtodeliverSWxproducts(basedonrecentsciencefindings),whereb)andc)shouldalsoaddressparticularnationalandtrans-nationalrequirements,andeventuallyfeedbackintonewchallengesforthescienceeffortsundera).Tothisendaconstantround-tableofdialoguebetweenallSWxpartners,i.e.SWxscientists,EuropeanPolicyMakers,publicandprivateSWxserviceorganisationsand representativesfromtheusercommunitieswillberequiredatsuchdiscussions.The decentralised ESA SSA approach of distributed and networked SWx Expert ServiceCentre’s for various parts of the coupled Sun-Earth system (still under development), is apromisingapproachtowardsthedevelopmentoffutureEuropeanSpaceWeatherPredictionCentres-bothfulfillingtheaboverequirementsandmakingthebestuseofthedistributedEuropeanexpertiseandcapabilities.RecommendationsinArea5:AEuropeanSWxeffortshould

1. utilise and coordinate existing national efforts toprovide regional spaceweatherservices(Examples:Belgium:ROB&VSWCM,UK:Met-Office,France:OFRAME,Italy:INSWSN)

2. involveESA,EU/ECandallmember-states,andmustbedrivenbytheEuropeanuser

requirements,asdiscussedinChapter4.

3. be conductedalso in close coordinationand cooperationwith thealreadyongoingparallel developmentson theglobal scale (UN-COPUOS), andwith efforts of othernations(US,China,Russia,Japan,etc…)

4. benefit from the experience in the development of global services and 24/7

operationsofexistingglobalorganisationssuchasWMO,ICAO,….

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5. involve Expert Scientists in the development of future European SWx services so

theseservicesbecomeandremaincompetentintheplasma-physicalcontextoftheSun-EarthSystem.

6. build on and expand the present decentralised and distributed ESA-SWE Expert

ServiceCentre(ESC)approachasagoodexampleforsuchefforts.

7. updatetheresultingEuropeanUserRequirementDocumentonatimescaleof3-5years-toadapttoemergingneedsoftheusercommunity.

2.6. Area6:Defineand implementanetworkof spaceandground-

basedassetsforfutureSWxobservationsCurrently space-weather related activities benefit enormously from a unique and existingfleetofscientificspacecraftobservingthesun,theheliosphereandgeo-space,supportedbya multi-facetted network of complementary ground-based measurement infrastructure.Theseassetscanstillsupportmostoftheinternationaleffortstodriveforwardandsupportan improved knowledge in the science of space weather processes (see our findings inChapter 1). While unique in its kind the present fleet of science-oriented spacecraft ingeospaceandtheheliosphereisneverthelessageingandobviouslyitalsodoesnotfulfiltherequirementsofafutureoperationalsystemforspaceweatherservices.Asone itemofparticular concernwewould like topointout thatmost current EuropeanSWxservicesrelyondatafromageing infrastructuresuchase.g.ESA‘sSOHOspacecraft incollaboration with NASA. SOHO is rapidly approaching its 25th anniversary, having thussubstantiallyexceededitsdesignlifetimeof2(!)years.WhileESAisindeeddiscussingwiththeUSthecoordinateddevelopmentofacommonspaceweathermonitoringsystem,thereistodatenoconsolidatedplanyetforthesuccessoroftheSOHOcoronagraphs.In contrast, the present day ground-based scientific networks of SWx instruments canprovide reliableoperational servicedata for future spaceweather services,however, theystillhavemajorgapsinbothcoverageandtemporalresolution;theyoftenlackcoordinationbetweencountriesandregionsandreal-timedataavailability.Alsotheyarerapidlyageing,oftenbarelysurvivingonscatteredanddecreasingnationalfunding.Thus we find that there is a clear urgency, indeed, to use the present scientific spaceweather assets in space and on the ground to make scientific progress towards thedefinitionofaneffective,efficient, and sufficientglobalobservational system.This in turnneedstobeoperatedinconcertbyseveralstakeholdersinspaceandontheground.ItwillalsobeimportanttodefinewhatkindofandexactlywhichSWxrelevantparametersin the interconnected various plasma regimes of the Sun - Heliosphere - Geospace -Atmospheresystemwillhavetobemeasured.Thecontent,locationandrequiredtemporalresolutionofsuchmeasurementsneedstobetunedtotheevolvingrequirementstodrivethenewlydevelopedadvancedSWxpredictionmodels.As an example we note the current collaboration between Europe and the US oncoordinatedspaceweathermissionstotheLagrangepointsL1andL5,alsotoillustratewhatcanbeachievedbycoordination.ThecombinationofcomplementaryobservationsfromL1and L5will enable better spaceweather forecasts, especially forecasts of CME arrivals atEarth.Thelatterisasimpleconsequenceofgeometry:observationsfromL5giveaside-on

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viewofCMEspropagating towardsEarth, such thatCME speeds canbedeterminedmoreaccurately,whilstobservationsfromL1arebetterplacedtodeterminewhenaCMEisearth-directed (see simple schematic at https://youtu.be/1Mv17P7hZ_Y). Furthermore amagnetometeratL5alsocanprovidevector-Bfromasecondperspectiveandthusresolvethe intrinsic ambiguity in the transverse field direction. Simultaneous remote solarobservations from L1 and L5 also provide increased surface coverage (particularly withearlier informationonwhat happenedon the far side) to improvebackground solarwindmodelling.ThisESAcollaborationwiththeUSisstronglysupportedandencouragedbythescience community in Europe and beyond. Recent scientific studies [e.g. 1, 28, 35] haveexploredtheadvantageofspaceweatherobservationsfromlocationssuchasL5.Inthiscontextwenoteexplicitlythatthisgeometryisquitedifferentfromotherorbitsandgeometriesrequiredforcutting-edgesciencemissions,suchasESA’sSolarOrbitermission.Itshowsthatnosinglemissioncanaddressallcombinedspaceweatherneeds.OfcourseitisobviousthatinparticularinthevariousGeospaceplasmaregimes–i.e.inthemagnetosheath, the magnetopause, the magnetotail and the inner magnetosphere (ringcurrentregionandupperionosphere)-SWxrelatedmissionscanandshouldnotaimatthecomplexityofscientificmulti-spacecraftmissionssuchasCluster,MMSorThemis.Inorderto satisfy future needs of systemwide relevant SWx observations, based on present andnewly derived knowledge from spaceweather enabling science, onewill need to identifyanddefinesimpler-orratherreduced-characteristicparameters,whichcanbemonitored24/7by fewerandsimplerspacecraftmissions inamoreeffectiveway.Suchmorereadilyavailableparameters (letus refer to themas so-called“Proxies” or rather“Essential SWxParameters”) should be able to describe the state of the plasma in the coupled spaceplasmaregimesatthesun,intheheliosphereandthroughoutgeo-spacesufficientlywell,sothat they can then be utilised to drive the necessary predictive models and to reachsatisfactorypredictionsabout theexpectedbehaviourof thecoupledsystem.However,aswehave illustratedabove, thescientificcommunitypresently lacksphysicalunderstandingof the Sun-Earth plasma system required to define such essential parameters sufficientlywell.OncesuchEssentialSWxParametershavebeendefinedtheycanadviseonthedefinitionoftheEuropeanportioninaglobalobservationaleffortforSWxpurposes.Thiswillimplyboththe provision of dedicated missions and ground-based assets to measure space plasmaparametersofrelevanceforspaceweatherwarningsandpredictions.Inclosecoordinationbetweenspaceagencies,andperhapsspaceweatheragencies,andwithrespecttonationalandEuropeanspace-andground-basedinfrastructure,oneshouldaimtobuildasufficientnetwork of operational measurement capabilities satisfying European needs andcontributingtoaglobalnetwork(withaviewtoimplementingtherecommendationsinthedocumentontheroadmapfortheperiod2015–2025commissionedbyCOSPARandILWS[54]).This activity will have to include the development of a concept for space weatherinformation protocols, including a potential early warning system for identifying andcommunicatingpotentiallyorexistingsevereand/orcatastrophicspaceweatherevents,tobe implemented through the coordination of, and developed by, existing space weatherserviceprovidersandinternationalbodiesandthroughtheactivitiesofothernationalspaceweatherserviceproviders.

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Findings:Based on the emerging scientific understanding of space weather events and processes,scientistsandspaceagenciestogetherwillhavetodefineanessentialandoptimumsetofobservable parameters at the Sun and in the heliospheric, magnetospheric, ionospheric,atmospheric, and solid-Earth system,which are needed to characterise the energetic anddynamicalstateof themost importantelementsof theSun-Earthcoupledplasmaregimesandtodrivetherequiredforecastsoftheexpectedresponseofthesystemasawhole.Basedonsuchrequiredsetsofobservablesonewillhavetodefinebothabaselineandanoptimum network of space and ground-based instrumentation, which canmonitor suchrequiredparameterswithsufficientaccuracy,24/7andinreal-time.We stress, however, that any future observational network must be able to do (a little)better thanthebareminimumSWxrequirementand-outofprinciple -alwaysalsoallownew science to emerge in order to prepare for potentially growing future SWx userrequirements.Any futureEuropeannetwork for spaceweatherobservations in spaceandon thegroundshouldalsobeembeddedinandbecoordinatedwithaglobaleffortofotheragenciesandnations-coordinationimpliesbothcomplementarityandcomparabilityintermsoflocation,type of measurement, and inter-calibration. The planned ESA Lagrangemission to L5 forimprovedsolarandsolarwindmonitoringinconcertwithotherinternationaleffortsatL1isagoodexampleforsuchcoordination.However, there will still be a need for additional purely scientific and space weatherenablingmissionsforanincreasedunderstandingoftheprocessesintheSunEarthsystem.Thiseffortcannotbereplacedby24/7operativemissions,inparticularnotiftheyareaimedattheobservationsofessentialSWx-parametersorproxiesonly.RecommendationsforArea6:DirectedtowardsESA:

1. Create a Forum between SWx scientists, staff of the ESA-SSA and ESA-SCIprogrammesandthespaceagenciesofindividualmemberstatesforthedefinitionandfutureoperationofa“fleet”ofdedicatedspacecraft:largecrucialcornerstonemissions,smallsatellitesatkeylocationsandhostedpayloadelementsforEuropeanSpaceWeatherpurposes.

2. Forthisdedicated“fleet”ofSWxspaceassetsdefineasetofobservables,fulfilling

the present user requirements and at the same time allowing for future sciencedevelopment to allow for an increased knowledge base for future emerging SWxrequirements.

DirectedtowardsEU,MemberStates,FundingandCivilProtectionAgencies:

3. On the basis of such considerations and in collaboration with individual memberstates support the maintenance, modernisation and future augmentation ofground-based instrument networks for space weather purposes to support thespaceassetsforSWxobservations.

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4. Eachtypeofmission,payloadorG-B instrumentnetworkshouldbecomepart of aspecifictypeofEuropeanand/orglobalnetwork- Examples of network “types”: Solar observations, solar wind observations at

L1/L5, and various Geo-space regimes: Magnetosphere, Ionosphere,Atmosphere,Ringcurrent.

- PresentG-Binstrumentnetworkscomprise:- Magnetometer networks and coordination through SuperMAG, coherent radar

systems SuperDARN, TEC-receivers, Ionosondes, Incoherent scatter radars likeEISCAT-3D,solarradio-observations,LOFAR,GONG,NMDB,etc.

NOTE:Alldata in this combined spaceandground-basednetworkof SWxassets systemshould be collected and disseminated under an Open Data Policy - and for potentialparallelscientificuseitshouldevenincludetheoriginalrawandS/Chousekeepingdata.

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3. Conclusions,OverarchingRecommendationsandFutureProspectsIn this reportwe have argued that - as in the rest of theworld - there is also an urgentEuropeanneedforcoordinationofSpaceWeathereffortsinindividualcountriesaswellasinand among European organisations such as the European Space Agency (ESA) and theEuropeanUnion(EU).Thiscoordinationshouldnotonly improveourability tomeetspaceweather risks, but also enable Europe to contribute to on-going global space weatherefforts.While space weather is a global threat which needs a global response it alsorequires tailored regional and trans-regional responses that require coordination at alllevels.We have shown that there are six essential and indispensable activities, which urgentlyrequirecoordinationatEuropeanlevel:

1. EnablingcriticalsciencetoimproveourscientificunderstandingofSWx:Our overall description of the coupled Sun-Earth system in the space age stillcontainscriticalgapsinthescientificunderstandingofseveralmechanismsthroughwhich space weather couples from space all the way down to Earth. Whilesignificant progress can and will be made using existing scientific infrastructureincluding existing multi-spacecraft missions and ground-based networks, supportmust urgently be provided for the next generation space missions and thereplacement and where needed targeted expansion of ageing ground-basedinfrastructure.

2. Development and coupling of advanced models by applying a system-science

approachwhichutilisesphysics-basedmodelling:Develop better physics-based models and also define metrics that facilitateassessmentofdifferentmodelsandtoencouragetheirtransitiontooperations.

3. AssessmentofrisksatNational,RegionalandEuropeanlevels:

EuropeanStatesshouldregularlyassesstheirexposuretoSWxrisksandcoordinateand combine their studies at regional and European level to cover theinterdependency of technological infrastructures. This requires close cooperationbetweendecisionmakers,SWxscientists,serviceproviders,andend-users.LessonslearnedshouldbesharedamongstallEuropeanstakeholders.

4. ConsolidationofEuropeanUserRequirements

EuropeanSWxuserrequirementsshouldbe(re-)assessedandprioritisedtakingintoaccountregionalandsocietaldifferencesandneeds,alsoaddressingdifferentneedsofvariousinfrastructuresystems.Thisshouldbedoneonaregularbasis,e.g.every5years,alsotofacilitatetheexchangeofinformationamongEuropeanSWxactors.

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5. SupporttoR2OandO2R

The best available knowledge and models should be used in future SWx serviceorganisations. Such transition from Research to Operations should be guided byteams of scientists all over Europe - following the distributed ESA Expert ServiceCentreapproach.

6. DefineandimplementanoperationalnetworkforfutureSWxobservations

Basedonour present scientific understanding and the above assessments of risksanduserrequirementsweneedtodefineanoperationalspace-andground-basednetworkthatmeasuresessentialspaceweatherparameterswhichinturncandrivetheSWxpredictionsrequiredtoprotectoursociety’sinfrastructure.

Wealsoidentifiedanumberofotherissuesrequiringattention:Afirstanalysisofknowledge,observationalgapsandrequirementsforanappropriateSWxwarningsystemwithspecialconsiderationofEuropeanSWxvulnerabilitiesandweaknesses,butalsotakingintoaccountEuropeanstrengthshasbeencarriedoutbytheExpertGroupsin the ESA SSA Space Weather Service Network. The results of this analysis have beenreviewedbytheEuropeanSpaceWeatherWorkingTeam.However,continuouselaborationoftheanalysisincludingassessmentofspaceweatherrisksonEuropeaninfrastructureandunderstanding of the user needswill be required because of the constantly evolving enduserlandscapeandEuropeanSWxcompetencies.WefindthatthepresentlyongoingSWxeffortsinEuropearetolargedegreeuncoordinatedandalsomostlyunsustainable.Thisisprobablyatleastpartiallyduetothefragmentationoffunding responsibilities in Europe. Apart from the ESA and the EU, individual states andmanydifferentagenciesalsofundspaceweatheractivities.TheESAispresentlydevelopingpre-operationalSWx-servicesintheframeworkofitsSpaceSituational Awareness (SSA) Programme with 19 out of ESA’s 22 Member Statesparticipating in the SWx segment. However, the ESA SSA programme is optional and theparticipating member-states contribute very diverse voluntary annual contributions, notalwaysreflectingNetNationalIncome.Alsothescopeoftheservices,establishedwithinthisprogramme,iscurrentlylimitedtotesting,verificationandvalidation.The EU had – and still has - scattered H2020 (FPx) SWx calls, reoccurring every other orsometimesevenonlyeverythirdyear.EveniftheEUfundingtoSWxactivitiesaddsuptoaconsiderableamountofapproximately60M€overthelast10years,thefundingofferedineach call is sub-critical to develop sustainable science and service activities, and did notmatchtheEuropeanneeds.Manyof thesecallswere (andstillare)aimedprimarilyat theprototypingofserviceswithrelatively littleregardforthescientific foundations,whicharerequired for suchservices tobecomereliable.Mostof thework required for thescientificunderpinningofSWx,especiallythescienceanddataexploitationactivities(seeourfindingsbelow),fallintothegeneralEU-calls,wheretheycompetewithotherfiledsofbasicscience.Additional funding provided by individual European states is fragmented, localised, un-coordinated,andalsomostlyinsufficienttosatisfythegrowingsocietalneeds,forboththeadvancement of knowledge and the provision of services. Also it is difficult to buildtransnational and regional efforts on national funding. Moreover, the private sector isrecentlybecomingmoreandmoreactiveinspace,andrealisesitsexposuretoSWx-threats.

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However-andyetagain-thefundingemergingfromsuchsourcesisoftentoodirectedandtopicallyfartoonarrowtosatisfySWxneeds.We would like to stress that while this diversity in funding is currently often seen as aEuropeanweakness, itcouldbeturned intoastrength, if itwerecoordinatedaccordingtotheprinciple„Letthosedotheworkwhoarebestatit“.WestronglyadvocateadedicatedEurope-widecoordinationofSWxactivities.ThiscouldbedoneinasimilarmannertohowtheCOPERNICUSprogrammedealswithEarthObservations.Manycountriesaredevelopingincreasinglysophisticatedinfrastructure,whichatthispointcan still be better prepared against SWx risks. This is a crucial step towards making ourmodernandtechnology-reliantsocietysustainableandresilient.OutsideEuropesucheffortsshould embrace developing nations, where such preparations are especially timely andefficient.FinalRecommendations:Europe should collaborate with other global partners (which work with different fundingstructuresandopportunities)toreapmutualbenefitsandrespondandcontributetoparallelworld-wideinitiativesfromglobalorganisationsase.g.theUnitedNations:

• The ESA and the EU need to coordinate their efforts and share the Europeanresponsibilities for SWx activities: science and research support, observations andservice as they do for other global issues, such as the Copernicus and Galileoprojects.

• The ESA in particular should take care of dedicated operational SWx missions,

hosted instrumentation, data production and dissemination – and continue todevelop initial service functions on the basis of the presently on-going model ofdistributedExpertServiceCentres,ESCs.

• The EU should complement ESA’s efforts by stimulating and funding overarching

SWxscience&dataexploitation inacontinuousandsustainable fashion. It shouldcoordinate or support additional space and ground-based SWx efforts inmemberstates or groups of member states, which are located under or at the magneticfootprintsofcertainspaceplasmaregimesorinparticulargeographicalregionsandsocanserveparticularSWxobservationalrequirements.

• Member-statesandlocalgroupsofmember-statesshouldcoordinatetheirnational

effortstosupporttheoverarchingactivitiesofESA/EUwithrespecttonationalandregionalprioritiesandabilities.

• AnydedicatedEuropeanSWxorganisationmustservefuturesocietalneeds,based

primarilyonEuropeanrisksandconsequentuserneeds,but inglobalcoordinationandwiththecontinuedsupportfromthesciencecommunity.

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