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J. Büchner Max-Planck Institut für Aeronomie, Lindau in collaboration with the CLUSTER data teams:

Current Results of the Investigation of Thin Current Sheets and Reconnection by Simulation and CLUSTER Observations. J. Büchner Max-Planck Institut für Aeronomie, Lindau in collaboration with the CLUSTER data teams: RAPID (P. Daly, U. Mall, B. Nikutowski; MPAe)

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J. Büchner Max-Planck Institut für Aeronomie, Lindau in collaboration with the CLUSTER data teams:

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  1. Current Results of the Investigation of Thin Current Sheets and Reconnection by Simulation and CLUSTER Observations J. Büchner Max-Planck Institut für Aeronomie, Lindau in collaboration with the CLUSTER data teams: RAPID (P. Daly, U. Mall, B. Nikutowski; MPAe) FGM (K.-H. Glaßmeier, K.-H. Fornacon; TUB) CIS (H. Reme; TOULOUSE and A. Korth; MPAe) J. Büchner WSEF Adelaide, July 25, 2002

  2. Outline Space Weather Relevance of current sheets and reconnection Necessity of kinetic approach Kinetic simulation results: from 2 to 3D CLUSTER observations J. Büchner WSEF Adelaide, July 25, 2002

  3. Reconnection – explained at Sun 1.) Ideal plasmas (ideally conducting): • magnetic flux frozen-in • magnetic connectivity conserved (A-B) 2.) Reconnection: • due to local non-ideality: • change of magnetic connectivity (C) J. Büchner WSEF Adelaide, July 25, 2002

  4. Current Sheets and Reconnection in Space Weather, Observed by Spacecraft J. Büchner WSEF Adelaide, July 25, 2002

  5. Current Sheet Particle Motion J. Büchner WSEF Adelaide, July 25, 2002

  6. Harris-type Current Sheet Model J. Büchner WSEF Adelaide, July 25, 2002

  7. 2D Kinetic Reconnection: Differential Ion / Electron Flows Electron outflow c/pe wide Ion outflow c/pi i wide J. Büchner WSEF Adelaide, July 25, 2002

  8. 2D Kinetic Reconnection: Hall currents cause quadrupolar By Current j due to differential e/i flows Quadrupolar magnetic field By J. Büchner WSEF Adelaide, July 25, 2002

  9. 2D Simulation Results (GEM 2001) (from:Birn et al: GEM effort 2001) • all these approaches break the frozen-in condition differently but yield identical reconnection rates • MHD reconnection is too slow by orders of magnitude, it is not adequate for collisionless magnetic reconnection J. Büchner WSEF Adelaide, July 25, 2002

  10. Wind s/c Observation in the Geotail Oeierset, et al., 2001 J. Büchner WSEF Adelaide, July 25, 2002

  11. 2.5 D Reconnection: Magnetopause 210 degrees: 2.5 D 125 degrees: 2.5 D 180 degrees: 2D Different shear angles between Magnetosphere and Magnetosheath -> (J = direction of the sheet current and of the reconnection electric field) J. Büchner WSEF Adelaide, July 25, 2002

  12. From 2D to „2.5D“ (Finite Byo) Quadrupolar By field Core field Byo -> flux ropes -> Bending of B-fields J. Büchner WSEF Adelaide, July 25, 2002

  13. Third Dimension: Variations in the Current Direction Enabled: ->LHD, Kink- and Sausage Instabilities J. Büchner WSEF Adelaide, July 25, 2002

  14. 3D Current Sheet Instability Isodensity surfaces; (Büchner and Kuska, 1999) J. Büchner WSEF Adelaide, July 25, 2002

  15. 3D: Sausage Mode Instability J. Büchner WSEF Adelaide, July 25, 2002

  16. 3D Kink Mode Instability J. Büchner WSEF Adelaide, July 25, 2002

  17. 3D Plasmoid Formation: (Büchner, 99) J. Büchner WSEF Adelaide, July 25, 2002

  18. The Cluster mission J. Büchner WSEF Adelaide, July 25, 2002

  19. Simulated Current Sheet Crossing J. Büchner WSEF Adelaide, July 25, 2002

  20. Cluster Orbit 7.9.01 18:00-24:00 J. Büchner WSEF Adelaide, July 25, 2002

  21. Magnetic fields 7.9.01 19:00 – 23:00 J. Büchner WSEF Adelaide, July 25, 2002

  22. Neutral sheet crossings 7.9.2001 19:00 – 23:00 UT J. Büchner WSEF Adelaide, July 25, 2002

  23. Current sheet thickness C1<->C4(19:00~>23:00) J. Büchner WSEF Adelaide, July 25, 2002

  24. The Four Spacecraft at 21:00 J. Büchner WSEF Adelaide, July 25, 2002

  25. Current sheet waves ~21:00 UT J. Büchner WSEF Adelaide, July 25, 2002

  26. Consequence: Multiple Reconnection (21:30-22:08) J. Büchner WSEF Adelaide, July 25, 2002

  27. RAPID – C1 protons 28-69 keV 7.9.01 21:45-22:02 UT J. Büchner WSEF Adelaide, July 25, 2002

  28. RAPID – C3 protons 28-69 keV 7.9.01 21:46-22:03 UT J. Büchner WSEF Adelaide, July 25, 2002

  29. RAPID – C4 protons 28-69 keV 7.9.01 21:46-22:03 UT J. Büchner WSEF Adelaide, July 25, 2002

  30. Summary Kinetic simulation revealed -> In a full 3D consideration thin current sheets (TCS) cause bulk waves triggering 3D reconnection CLUSTER multipoint measurements allowed -> first independent determination of CS thickness and motion Results: CS thinning (->TCS) leads to the predicted wave activity Extreme CS thinning is followed by reconnection J. Büchner WSEF Adelaide, July 25, 2002

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