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Magnetic connectivity associated with SW reconnection events: STEREO/SWEA

Benoit Lavraud , 1 Andrea Opitz, 1 Jack Gosling, 2 J.-A. Sauvaud, 1 and the IMPACT team 1,3,4,5 1: CESR/CNRS, Toulouse, France 2: LASP, Boulder, Colorado, USA 3: SSL, U. Berkeley, USA 4: UCLA, Los Angeles, USA 5: NASA/GSFC, Maryland, USA, ….

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Magnetic connectivity associated with SW reconnection events: STEREO/SWEA

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  1. Benoit Lavraud,1 Andrea Opitz,1Jack Gosling,2 J.-A. Sauvaud,1and the IMPACT team1,3,4,51: CESR/CNRS, Toulouse, France2: LASP, Boulder, Colorado, USA3: SSL, U. Berkeley, USA4: UCLA, Los Angeles, USA5: NASA/GSFC, Maryland, USA, … Magnetic connectivity associated with SW reconnection events: STEREO/SWEA

  2. The STEREO Solar Wind Electron Analyzer (SWEA) instrument • SWEA instruments identicalon ST-A and B • Preliminary inter-anode and inter-deflection calibrations • Pitch angle distributions should be OK in relative sense • Refinements still to be done, as well as absolute calibrations TOSUN Solar wind Solar Wind e- Electrostatic deflector Electrostatic analyzer

  3. Suprathermal (>200 eV) electrons are very fast: 1AU in a matter of hours •  Magnetic topology • Check whether pitch angle distributions are compatible at ACE and STEREO • The case of solar wind reconnection events is most useful: complex and variable PADs over short periods MOTIVATION : Solar wind Heliospheric Current Sheet (HCS) [Gosling et al., 2005; 2006]

  4. Spacecraft locations on March 31, 2007 HCS = Heliospheric current sheet SUN Solar wind No SWEA dataat STEREO Aunfortunately

  5. HCS reconnection layer at ACE/WIND HCS Solar wind

  6. HCS reconnection layer at ACE/WIND RED: distribution inside the layer Solar wind  ACE & WIND are Sunward of X-line on closed field lines connected to the Sun

  7. Heliospheric current sheet reconnection layer at ST-B (Arb. Units) Solar wind Reconnection layer  Marked differences in pitch angle distrib. inside the layer

  8. Closed field lines observed at STEREO-B as well Note: Absolute PSD values are off, but relative behavior is meaningful Red: PAD inside layer Solar wind (Arb. Units)  ST-B also sunward of X-lineNext: find event with X-line in between…

  9. Closed field lines observed at STEREO-B as well (Arb. Units) Solar wind Mixed suprathermal electrons not bound to the layer Reconnection layer  Evidence for the separatrix layer outside the exhaust

  10. Closed field lines observed at STEREO-B as well Solar wind Suprathermal electrons from the other side • The existence of separatrix layers is confirmed for this event, although it is not always observed (?)

  11. Some topics of interest • Continuous nature of reconnection • X-line spatial extent • Particle acceleration/heating at X-line • Particle heating at exhaust boundaries All of the above potentially different at Earth’s magnetosphere !?

  12. CONCLUSIONS : • Although additional corrections are still to be done, SWEA pitch angle data are meaningful • The case of solar wind reconnection events is most useful for that purpose: complex and variable • SWEA observations of high energy electron leakage confirm that the boundaries of the reconnection layer are open, as expected • Other interesting topic: Is heating occurring at the boundaries? Different from Earth’s magnetopause? Solar wind

  13. MOTIVATION : • Check whether pitch angle distributions are compatible at ACE and STEREO • The case of solar wind reconnection events is most useful: complex and variable • We may observe the change in connectivity between widely separated spacecraft • For reconnection events in between the spacecraft we may contribute to the debate about strahl disappearance Solar wind [Gosling et al., 2005; 2006; Crooker and Pagel, 2008]

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