anti-parallel versus component reconnection at the magnetopause

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Anti-parallel versus Component Reconnection at the Magnetopause. K.J. Trattner Lockheed Martin Advanced Technology Center Palo Alto, CA, USA and the Polar/TIMAS, Cluster/CIS, Image/FUV teams. Outline. Reconnection: When, Where and Why Where: The Cusp for Northward IMF - PowerPoint PPT Presentation

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  • Anti-parallel versus Component Reconnectionat the MagnetopauseK.J. TrattnerLockheed Martin Advanced Technology CenterPalo Alto, CA, USAand thePolar/TIMAS, Cluster/CIS, Image/FUV teams

  • OutlineReconnection: When, Where and WhyWhere: The Cusp for Northward IMF- Anti-parallel Reconnection- Component ReconnectionWhere: The Cusp for Southward IMF- Component Reconnection- Anti-parallel ReconnectionSummary

  • Magnetic ReconnectionWhen does reconnection occur all the time (i.e., it is a quasi-steady process)We have poor knowledge of the changes in the reconnection rateWhere does reconnection occur recent observations appear to favor anti-parallel reconnection but some previous observations suggest component reconnectionWork in progress. Stay tuned!Why does reconnection occur DONT KNOW!The answer appears to be in the electron diffusion regionFuture mission (e.g., MMS) will have the time resolution and instrumentation to fully investigate this region

  • Magnetic Reconnection Near the Earth: Field Line Topologies (for Southward IMF)Blue - Solar Wind Field LinesGreen - Closed Field LinesRed - Open Field LinesFocus on dayside reconnectionMagnetopause Current Sheet

  • Observe Reconnection In Two LocationsCusp: foot of the reconnected field lines Does reconnection stop? Where does reconnection occur?Magnetopause: up close and personal What is the reconnection rate? Where does reconnection occur?Each location hasits advantagesand disadvantages

  • When is Magnetic Reconnection Occurring?

  • WHENCusp Ion Energy Dispersion for Southward IMF

  • MLT = 3hUT = 5hTrattner et al. [2002]WHEN:Low- and High Altitude Cusp Observations

  • Direct Confirmation of Images of the Foot of a Reconnecting Field Line Images of the footpoint from the IMAGE spacecraft

    Simultaneous observations at the reconnection site from the Cluster spacecraft (bi-directional ion flows)

    Magnetic field mapping confirms the location of the ionospheric spotObservations Mapping

  • Does Reconnection Stop? You Decide..

  • IMF Rotation from North to South: Observations and PredictionsAlthough there is a delay, in general, there isa simple change in the location of the reconnection site

  • IMF Rotation from South to North: Observations and PredictionsSimilar for south to north transition a delay but reconnectiondoes not stop, even when conditions change

  • Where is Magnetic Reconnection Occurring?

  • WHERE is reconnection occurring? boils down to twomodels.

  • Remote Sensing the High Latitude Reconnection SiteMagnetopauseSunward Convection ProducesTwo Effects:Auroral Spot in the IonosphereVelocity Dispersion in the CuspIMAGEspacecraft

  • Proton aurora images from IMAGE/FUV taken just before and after the arrival of an interplanetary disturbance in the ionosphere.Fuselier et al. [2002]

  • Mapping cusp foot points along geomagnetic field lines into the magnetosphere (Fuselier et al. [1994]).

  • Comparison of the location of field lines mapped from the cusp foot points with the location of anti-parallel reconnection sites.

  • The Location of the Reconnection Line for Northward IMFPolar/TIMAS Cusp Crossings240 Cusp Events for Northward IMF.81 events analyzed.Calculate the Distance to the X-Line.Mapping the Distance along the Geomagnetic Field.

  • Cusp Ion Energy Dispersion for Northward IMF

  • Ion Dispersion in the Cusp: Distance to the Reconnection SiteAssumes: Instantaneous Acceleration Simple Field Line Structure

  • Xr/Xm = 2Ve/(Vm-Ve)Onsager et al. [1990]Fuselier et al. [2000]

  • The Location of the Reconnection Line for Northward IMFEvent 1: Sept. 22, 1997

  • Time (UT)Convection time to the MP: 22min

  • Tsyganenko [1996] together with Cooling [2001] IMF draping model

  • The Location of the Reconnection Line for Northward IMFEvent 2: Oct. 30, 1997

  • 81 events analysed67 events with useable 3D cutoffs29 antiparallel, 23 component, 15 >>Bx

    -Bx, +By+Bx, +By-Bx, -By+Bx, -ByAntiparallelReconnection29 events9 events

    1200-1430MLT15 events

    0900-1200MLT5 events

    1000-1140MLTComponentReconnection23 events3 events

    0830-1030MLT2 events

    0930-1130MLT2 events

    1700-1730MLT16 events

    1700-1730MLT

  • Southward IMF: Anti-Parallel and Component ReconnectionCan we determine the distance THAT accurately?View from the Sun

  • Precipitation is Different for the Two Types of ReconnectionAnti-Parallel

    Tilted Line

    The KeyDifference isThe Flux NearNoon

  • Fuselier et al. [2002]

  • Example: Double Cusp Interval Component or Anti-Parallel?Trattner et al. (2003)showed these arespatial features(energy-time(latitude) dispersion indicative of reconnection)

    Compute the distanceto the reconnection sitefor the two dispersionsand see if they aredifferentFirst dispersion Second dispersion

  • Two Different Distances for the Two DispersionsView from the SunFirst Dispersion Second DispersionThe second dispersionoccurred closer to thespacecraft than thefirst dispersion

    Compare these distancesto predictions from anti-Parallel reconnection(One distance for eachmeasured distribution function)Cluster

  • How Do the Distances Compare with Anti-Parallel Reconnection?Second Dispersion First DispersionRed = Anti-ParallelReconnectionDoesnt compareExactly with Anti-Parallel ReconnectionGet Some Help With the Interpretation.

  • The Cusp Images Tell the DifferenceLooks more like anti-parallel reconnectionbut with a shift relativeto local noonObservationsAnti-Parallel Tilted Neutral Line

  • Conclusion: Anti-Parallel Reconnection (with a Local Noon Shift)Second Dispersion First DispersionThe pure T96 modeldoes not show howthe northern hemispherereconnection line isshifted ~1/2 hour pre-noon

    However, the cusp imagesdo!

  • SummaryNORTHWARD IMF: Image/FUV and Polar/TIMAS observations reveal that both reconnection scenarios occur simultaneously.

    SOUTHWARD IMF: Both reconnection scenarios observed. Unclear what triggers one or the other.

  • WHEN: Multiple Cusps

  • Anti-Parallel Reconnection for Northward IMFantiparallel reconnection sitesZmagnetosheath fieldcuspsYView of the Dayside magnetopause from the SunMagnetopauseEarth's Magnetic Field in the MagnetosphereSolar Wind Magnetic FieldSolar WindNorthward IMF

  • Northward IMFPoleward Reconnection SiteEquatorward Reconnection SiteObservations in the cusp have indicated the possibility of component reconnection fornorthward IMF (e.g., Onsager and Fuselier, 1994; Chandler et al., 1999; Fuselier et al., 2000)

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