Magnetotail Current Sheet IKI 26-30 September 2011 Magnetic Reconnection in the Current Sheet:

1. Magnetotail Current Sheet IKI 26-30 September 2011 Magnetic Reconnection in the Current Sheet: Geotail Observations Wednesday 28 September 2011, 1220-1300 T. Nagai Tokyo Institute of Technology

2. The basic physical components on the magnetic reconnection site • The central electron current layer – the (electron) diffusion region • The ion-electron decoupling region – the Hall physics region • Inflows and Outflows – the MHD region

3. MHD Picture of Magnetic Reconnection inflow outflow Bz > 0 Bz < 0

4. Particle Picture of Magnetic Reconnection Ion flows Electron flows unit ViA unit VeA

5. Hall Magnetic Fields

6. Outflows Ve Ve Vi Vi Bz > 0Bz < 0 MHD Ion-electron decoupling MHD

7. electron current layer - Vey Bz > 0Bz < 0

8. The basic physical components on the magnetic reconnection site • The central electron current layer – the (electron) diffusion region • The ion-electron decoupling region – the Hall physics region • Inflows and Outflows – the MHD region

9. 0700 UT

10. electron Vx ion Vx ion Vy electron Vy

11. electron Vx ion Vx ion Vy electron Vy electron Vperp x electron Vperp y 2 10 nA/m

12. 0630 UT

13. ion Vx ion Vy electron Vx electron Vy

14. electron Vx electron Vy electron Vperp x electron Vperp y 2 20 nA/m

15. 1055 UT

16. electron Vx ion Vx ion Vy electron Vy

18. Geotail Observations in the Plasma Sheet (plasma b > 1) in 1994-2010 X = -18 to -30 RE Y = -20 to +20 RE

19. MHD flows Vi = Ve Errors are small when energetic electrons are rich. electron Vx ion Vx electron Vy ion Vy

21. Tailward Flows with Bz < 0

23. Tailward flows with Bz < 0

24. Reconnection events

25. Physical Size of the Magnetic Reconnection Site in the X direction in the Y direction ?

26. 15 May 2003 near 1055 UT the spacecraft Geotail at 28 RE in situ observations of magnetic reconnection Geotail

27. Bz < 0 Bz > 0 Earthward flows Bz > 0Bz < 0 Tailward flows Ion Et Earthward flows Tailward flows

28. Main Targets of This Paper • Detect the central intense electron current layer • Get scales of magnetic reconnection • with Geotail observations • VA = 2,200 km/s • li = 1,200 km (ion inertial length) • Geotail MGF 16 vectors /s • LEP 12 s • electron g-factor 4x10 • DT 5.5x10 -4 -3

29. Bz < 0 Bz > 0 Earthward flows 5 minutes Bz > 0Bz < 0 Tailward flows Ion Et Earthward flows Tailward flows

30. Ion observations Bz > 0Bz < 0 Bz < 0 Bz > 0 Earthward flows 1000 km/s ion flow VA = 2200 km/s Tailward flows

31. Ion flows vs. electron flows Ion Et Bz > 0Bz < 0 Bz < 0 Bz > 0 Vi Vx > 3000 km/s electron flows Vy > 6000 km/s electron flows Ve Ve

32. Ion and electron flows perpendicular to the magnetic field Bz > 0Bz < 0 Bz < 0 Bz > 0 V Earthward flows Vx > 2000 km/s electron flows Vy > 3000 km/s electron flows Ve Tailward flows Ve

33. Electron observations acceleration and heating electron Et Bz > 0Bz < 0 Bz < 0 Bz > 0 V Vx > 2000 km/s electron flows Vy > 3000 km/s electron flows Ve Ve

34. Bz > 0Bz < 0 Earthward flows Tailward flows 1057:44 1053:44 UT time Earth tail Bz > 0Bz < 0 > 8.47 keV electron directional fluxes

35. Bz > 0Bz < 0 Earthward flows Tailward flows 1057:44 1053:44 UT time Earth tail Bz > 0Bz < 0 electron velocity distribution function In the equatorial plane Vy < 0 dawnward Vy > 0 duskward

36. Bz > 0Bz < 0 Earthward flows Tailward flows 1057:44 1053:44 UT time Earth tail Bz > 0Bz < 0 electron velocity distribution function Hall electrons

37. Bz > 0Bz < 0 Earthward flows Tailward flows 1057:44 1053:44 UT time Earth tail Bz > 0Bz < 0 ion velocity distribution functions

38. Bz > 0Bz < 0 Earthward flows Tailward flows time Bz > 0Bz < 0

39. Bz > 0Bz < 0 Earthward flows Tailward flows time counter-streaming inflows Bz > 0Bz < 0 ion velocity distribution functions

40. Important Questions ion-electron decoupling Ve >> Vi MHD MHD large Vey 1057:44 1053:44 UT intense electron current layer spatial scales?

41. Asymmetric outflows MHD flows +450 km/s -650 km/s Earthward flow speed tailward flow speed

42. MHD flows +550 km/s -550 km/s (+450 km/s) (-650 km/s) -100 km/s tailward velocity of reconnection site

43. Bz > 0Bz < 0 Earthward flows Tailward flows time counter-streaming inflows Bz > 0Bz < 0 ion velocity distribution functions

44. Asymmetric inflows inflows Vx = +64 km/s Vx= -269 km/s

45. inflows Cluster results -100 km/s Baker et al. 2002 Imada et al. 2007 Vx = +164 km/s Vx= -169 km/s (+264 km/s -269 km/s) -100 km/s tailward velocity of reconnection site

46. ion-electron decoupling region MHD MHD 1 li Earth tail central electron current layer 8 li Vx peak Flux peak Ion ele ele ion 8 li = 1.5 RE 1 li = 1200 km

47. the X-line position PIC simulation results the northern earthward side of the reconnection site (upper-left quadrant)

48. observation simulation at TΩi = 35 Vix / Vex 0.2-0.3 0.1 Vey / Vex 1.25 1.4 Vix 0.5 VA 0.3 VA the full extent of the central 1 li 1 li electron current layer the full extent of 8 li 8 li the ion-electron decoupling region

49. 8 li = 1.5 RE ion-electron decoupling region Geotail Survey of Tailward Flows with Bz < 0 in 1995-2003 209 events Nagai et al., 2005

50. Geotail Reconnection Events = Observations of Ion-Electron Decoupling Region 34 events 34/208 = 0.16 reconnection events at 20-30 RE Nagai et al., 1998; 2001