incoherent scatter radar as a tool for m-i coupling studies ian mccrea jackie davies sstd rutherford...
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Incoherent Scatter Radar as a tool for M-I coupling studies
Ian McCreaJackie Davies
SSTDRutherford Appleton
LaboratoryChilton,
Oxfordshire UK
Structure of this talk
• Why study the magnetosphere with radars ?– What can IS radars do ?– What can’t they do ?– What other toys do we need ?
• Cluster in particular– What did we start out to do ?– What have we actually done ?– What kind of science has come out ?– What do we still need to do ?
• What’s next ?– THEMIS, MMS and Cross-Scale– AMISR and EISCAT-3D
Why study the magnetosphere from the ground ?
• Converging field geometry projects very diverse regions to small areas: Ai ~ Am * (Bm/Bi)
• Measure boundaries and boundary conditions (e.g. conductivities, heating rates)
• Possibility for conjugate observations and time history of a field line
• Resolution of spatial and temporal effects
Strengths of ISRs• Backscatter is continuous in
range
• Continuous time series allows study of dynamics
• Steerability and flexible pulse-coding allow great freedom in experiment design
• Multi-parameter data sheds light on various aspects of MI processes
• Standard interpretation of features (OCB, PIFs etc)
Moen et al, Ann. Geophys., 22, 1973, 2004
Weaknesses of ISRs
• Limited by SNR, especially at long range
• Assumptions may not always work (non-thermals, composition)
• Limited viewing area, so lack of spatial context.
• Velocity determination not good in far field
• Ambiguity in moving events
Lockwood et al, Nature 361, 424, 1993
Lockwood et al, PSS, 36, 1229, 1988
Weaknesses of ISRs
• Limited by SNR, especially at long range
• Assumptions may not always work (non-thermals, composition)
• Limited viewing area, so lack of spatial context.
• Velocity determination not good in far field
• Ambiguity in moving events
Lockwood et al, Nature 361, 424, 1993
Weaknesses of ISRs• Limited by SNR, especially
at long range.
• Assumptions may not always work (non-thermals, composition)
• Limited viewing area, so lack of spatial context.
• Velocity determination not good in far field
• Ambiguity in moving events
Lockwood et al, Nature 361, 424, 1993
The Necessity of SUPERDARN
ISR and SUPERDARN observations are different, but strongly complementary
Both have their own strengths and weaknesses
Davies et al, Ann. Geophys., 20, 781, 2002
More from the toolbox
Combination of ISR and imager data shows correspondence of optical and radar features
Assimilative electrodynamics from magnetometers etc, and combination with ISR data
Lühr et al, Ann. Geophys, 14, 162, 1996
Carlson et al, GRL, 33, L05103, 2006
Cluster Science Topics
• Magnetopause reconnection and Flux Transfer Events
• Dynamics and structure of the cusp region
• Wave-particle interaction in the cusp
• Formation and properties of the LLBL
• Large-scale waves at the flank magnetopause
• Particle acceleration during magnetotail reconnection
• Dynamics and properties of magnetotail current sheet
• Physics of magnetospheric substorms
• Structure of flux ropes in the magnetotail
The Original Modes
Cluster 1: June 4th 1996
ESR 500MHz ISR
ESR Cluster Experiments
• Uses 32m dish and interleaved 42m (4:1)• 42m dish is fixed field-aligned (az 182o, el 81o)• Cusp conjunctions use 32m radar in LowElNorth
mode (az 336o, el 30o)• Tail conjunctions often use 32m radar in
LowElSouth mode (az 167.7o, el 30o)• Tau0 modulation alternating code 20 s baud• Basic range resolution 3.0 km (~30 km in F-
region)• Basic time resolution 6.4s• Range coverage 119 To 1366 km• Mag. Latitude coverage 76o To 80o (Low El North)• Mag. Latitude coverage 74o To 67o (Low El South)
Tromso VHF Radar, 224 MHz ISR
VHF Cluster Experiments
• Radar pointed geographic north (azimuth 359.5o, 30o elevation)
• Dual beam experiments initially • Tau1 modulation scheme• Alternating code experiment (baud 24s)• Basic range resolution 3.6 km (typically 20 km in
F-region)• Altitude Coverage 77km to 1268 km• Mag. Latitude Coverage (67.7oN) 73oN to 80oN• Basic time resolution 5s (60s in analysis)• Standard analysis by GUISDAP
Cusp Sector:March 16 2006
• Footprints generally over Svalbard, or further North
• Emphasis on latitudinal coverage, flow transients etc.
• ESR continues latitude coverage north of VHF viewing area
• ESR field-aligned data provide a second perspective on plasma passing over Svalbard
Cusp Sector:March 16 2006
• February to April each year
• Emphasis on magnetopause crossings
• Conjugacy with Tromsø/ESR
• 4-hour experiments
• Consistency with SUPERDARN
• Hand-on to Sondy
• >70 EISCAT/Cluster cusp experiments since 2001
Cusp Sector Modes:
ESR Low El North, VHF Dual Beam CP4
Cusp Sector Modes:
ESR Low El North, VHF Single Beam CP4
Cusp Sector Modes
T
L
Tromsø
Range coverage 151 to 2100 km
Height coverage 77 to 1268 km
Mag lat coverage (67) 73 – 80oN
Geo lat coverage (73) 76 – 83oN
ESR
Range coverage 148 – 1295 km
Height coverage 76 – 737 km
Mag lat coverage 76o – 80o
Geog lat coverage 79o – 84o
Multi-radar dataPoleward Moving Forms4 October 2002
K.A. McWilliams, University of Saskatchewan
Tail Conjunction Modes
• Footprints generally between Svalbard and Tromsø
• Emphasis on coverage of auroral region
• VHF beam covers some latitudes north of ESR • ESR covers some latitudes sourth of VHF viewing area
• ESR field-aligned data see e.g. plasma emerging from polar cap
Tail Conjunction Modes:
ESR Low El South, VHF Dual Beam CP4
Tail Conjunction Modes:
ESR Low El South, VHF Single Beam CP4
Tail Conjunction Modes
TromsøRange coverage 151 to 2100
kmHeight coverage 77 to 1268 kmMag lat coverage (67) 73o – 80o
Geo lat coverage (73) 76o – 83o
ESRRange coverage 148 – 1295 kmHeight coverage 76 – 737 kmESR mag lat coverage 74o-67o
ESR geog lat coverage 77o-69o T
L
Perigee Passes
• Occur at all times of year
• Generally 2-3 suitable passes a month
• Frequently we do not cover these
• Same mode as cusp sector passes
• Should we do more ?
Flank Skimming/Flank Crossing Orbits
• Occur in the summer and winter
• Oriented for phenomena such as waves on the flanks
• Same mode as cusp sector passes
• Less frequent runs and less scientific interest in these months ?
Sondrestrom ISR1300 MHz
3 MW
32 m dish
Sondrestrom/Cluster Experiments
First Cluster Cusp Encounter
• First Cluster pass through the ionospheric cusp
• a) Magnetic field at ACE satellite orbiting upstream of the Earth at the Lagrange point
• d) Energy of the particles observed by Cluster
• b) and c) Ionosphere as seen by the radar in particular, strongly enhanced high density features (red) are clearly visible moving away from the radar
Polar Cap Patches under Bz South
Lockwood et al, Ann. Geophys., 19, 1589, 2001a
• Cluster outbound from tail lobe to dusk sector mantle
• ESR sees poleward-moving patches, repetition frequency ~ 10 minutes
• DMSP sees dispersed ion and electron signatures
• Patches also pass over Cluster
• Good correlation of low energy precipitation at EISCAT and low-energy sheath electrons at Cluster
• Suggests a mechanism more complex than time elapsed since reconnection for controlling soft particle flux
Reconnection under High Clock Angle
Lockwood et al, Ann. Geophys, 19, 1613, 2001b• IMF turns north at 0945 (1100 at
ionosphere)
• Remains generally north, with excursions to intermediate clock angle
• Cluster moving outbound through magnetosheath, with transient excursions into LLBL and cusp
• Excursions coincide with clock angle swings
• Poleward-moving transients seen at these times by ESR
• Could be FTEs - not classical signatures, due to position in interior cusp ?
Pulsed Reconnection in By dominated IMF
Wild et al, Ann. Geophys., 23, 2903 2005• Combines in-situ observations of pulsed reconnection by Cluster and Double Star.
• Pulsed flows directed poleward and dawnward
• Flux tubes anchored at mid-latitude and close to sub-solar point
• Reconnection not limited to high latitudes in By dominated IMF
• Cluster/FAST/Sondy/SUPERDARN
• Transient reconnection signatures at three altitudes
• Cluster goes from cusp to boundary layer during a pressure pulse
• Flow bursts seen at Cluster interpreted as Alfven waves in reconnection events
• FAST sees stepped cusp signatures correspond to flow bursts
• Sondy sees flow bursts poleward of convection reversal boundary
• OCB equatorward of CRB
• Momentum transfer in downstream boundary layer ?
Conjugate Reconnection at Multiple Heights
Farrugia et al, Ann Geophys, 22, 2891, 2004
Electrodynamics of Auroral Arcs
Aikio et al, Ann. Geophys., 22, 4089, 2004• Cluster in midnight sector at 4 RE
• Pseudo-breakup onset occurs
• Current sheets of equatorward arc widen and FAC doubles in < 2 mins
• Density cavity forms in the downward current region of poleward arc
• Pedersen current decreased, return current region forms a growing load for current circuit
• Electrons carrying return current accelerated and region widens to supply required amount of return current
• Evidence of Alfven wave acceleration of electrons in the upward FAC
Halloween StormRosenqvist et al, JGR 110, 2004JA010927
The Future:THEMIS, Cluster and the ISRs
The Future:MMS and Cross-Scale
The Future:The KuaFu Mission
EISCAT-3DEISCAT-3D Possible new sites
Possible new baseline
Transmitter site
69.4 N 30.0 E
69.58 N 19.22 E
68.2 N 14.3 E
~67 N
• A common transmitter facility with RX capabilities: A common transmitter facility with RX capabilities:
– Close to the present Tromsø (NO) EISCAT siteClose to the present Tromsø (NO) EISCAT site– Operating frequency in the (225-240) MHz rangeOperating frequency in the (225-240) MHz range– Power amplifiers utilising VHF TV power FETs Power amplifiers utilising VHF TV power FETs – Phased-array system with > 16 K elements, PPhased-array system with > 16 K elements, Ppkpk > 2 > 2
MWMW– Actual antenna configuration and performance TBD Actual antenna configuration and performance TBD – >3 outlier, RX-only array modules for >3 outlier, RX-only array modules for
interferometryinterferometry– Fully digital, post-sampling beam-forming on Fully digital, post-sampling beam-forming on
receivereceive– Comprehensive interferometric capabilities built-inComprehensive interferometric capabilities built-in
• 2 + 2 very large receive-only (”remote”) arrays:2 + 2 very large receive-only (”remote”) arrays:
– Actual siting TBD, four promising sites Actual siting TBD, four promising sites investigated...investigated...
– Filled apertures, long enough to provide ~ 1 km Filled apertures, long enough to provide ~ 1 km beam resolution at E region altitudes above beam resolution at E region altitudes above transmittertransmitter
– Medium gain (~ 10 dBi) element antennasMedium gain (~ 10 dBi) element antennas– Fully digital, post-sampling beam-formingFully digital, post-sampling beam-forming– Sufficient local signal processing power to generate Sufficient local signal processing power to generate
at least five simultaneous beamsat least five simultaneous beams– 10 Gb/s connections for data transfer and remote 10 Gb/s connections for data transfer and remote
control and monitoringcontrol and monitoring
Present idea of the EISCAT 3D system geometry. The central core (denoted by a green filled circle) is assumed to be located near the present Norwegian EISCAT site at Ramfjordmoen. The dashed circle with a radius of approximately 250 km indicates the approximate extent of the central core FOW at 300 km altitude. Receiving sites located near Porjus (Sweden) and Kaamanen (Finland) provide 3D coverage over the (250-800) km height range, while two additional sites near Abisko (Sweden) and Masi (Norway) cover the (70-300) km height range.
The EISCAT_3D Test Array The EISCAT_3D Test Array (“Demonstrator”)(“Demonstrator”)
• 200 m200 m22 filled array now being erected at EISCAT Kiruna filled array now being erected at EISCAT Kiruna site to provide facilities for validating several critical site to provide facilities for validating several critical aspects of a full-scale 3D receiving array in practice under aspects of a full-scale 3D receiving array in practice under realistic climatic conditions: realistic climatic conditions:
– Receiver front ends, A/D conversion (WP 4), Receiver front ends, A/D conversion (WP 4), – SERDES, copper/optical/copper conversion (WP 12),SERDES, copper/optical/copper conversion (WP 12),– Time-delay beam-steering (WP4 / WP9),Time-delay beam-steering (WP4 / WP9),– Simultaneous forming of multiple beams (WP 9),Simultaneous forming of multiple beams (WP 9),– Adaptive pointing (self-) calibration (WP 9),Adaptive pointing (self-) calibration (WP 9),– Adaptive polarisation matching (WP 9),Adaptive polarisation matching (WP 9),– Interferometry trigger processor (WP 5),Interferometry trigger processor (WP 5),– Digital back-end / correlator for standard IS (WP 9),Digital back-end / correlator for standard IS (WP 9),– Time-keeping (WP12)Time-keeping (WP12)
•• Array oriented in Tro-Kir Array oriented in Tro-Kir plane; plane; 48 short (6+6) element 48 short (6+6) element Yagis at Yagis at 5555oo elevation,elevation,
•• Center frequency of (224 ± Center frequency of (224 ± 3) 3) MHz allows reception of MHz allows reception of transmissions from existing transmissions from existing Tromsø VHF system.SNR Tromsø VHF system.SNR estimated to be sufficient for estimated to be sufficient for useful bistatic IS work (> 6% @ useful bistatic IS work (> 6% @
300 km, 1.0 10300 km, 1.0 101111 m m-3-3),),
• • The 55The 55oo elevation provides elevation provides coverage from ~ 200 km coverage from ~ 200 km
altitude altitude to over 800 km above to over 800 km above Tromsø.Tromsø.
D
D cos D sin
R1
R4
R12
N
D selected to make ( D sin ) optimal stacking distance
BEAM
DIRECTION
Conclusion
• CGBWG is helping to assemble a unique set of radar data for MI coupling studies (credit to Jim Wild, Gareth Chisham, Steve Milan and many others)
• Huge thanks are due to the staff at EISCAT and Sondy !
• All ISR data are on-line via Madrigal – http://www.openmadrigal.org/
• Cluster Ground-Based Working Group– http://www.ion.le.ac.uk/~cluster
• Feedback needed: – What else should the ISRs be doing ?– Are these the right modes ?– What modes are needed to support new missions ?
The End !!
What can IS radars do ?
• Add Lockwood slides – point out usefulness for dynamics, boundaries, temperature gives time history etc.
AA Operations in 2006
0
10
20
30
40
Jan
Mar
May Ju
lSep Nov
Ch
arg
ed
Ho
urs
KST
ESR
First Cluster Cusp Encounter
Wild et al 2005