Magnetic Reconnection in the Magnetotail

1. Magnetic Reconnection in the Magnetotail T. Nagai and M. Fujimoto Tokyo Institute of Technology

2. Pre-Geotail Era Signatures of Magnetic Reconnection Fast plasma flows with Bz < 0 or Bz > 0 in the MHD level MHD-code Simulations M. Ugai, T. Sato,…

3. Pre – Geotail Era IMP-6 October 1972 Hayakawa et al. (1982) Nishida (1984)

4. The Geotail Era The first near-Earth tail survey in the 1995/1996 winter season 1. Location of magnetic reconnection for substorm onsets Onsets on the ground Plasma flows in the tail 2. Structure of magnetic reconnection

5. Fast flows for substorm onsets 30 Re 20Re Nagai et al. (1998) Nagai and Machida (1998)

6. Location of Magnetic Reconnection Ieda et al. (1998) Machida et al. (1999) Miyashita et al. (1999) Ueno et al. (1999) R. Nakamura (1999) Miyashita et al. (2000) Machida et al. (2000) Miyashita et al. (2001) R. Nakamura et al. (2001) Ueno et al. (1999)

7. Structure of Magnetic Reconnection Ion and Electron Dynamics On the basis of velocity distribution functions Identify the magnetic reconnection event

8. Plasmoid at XGSM = -141.51 Tailward ions Tailward electrons Machida et al. (1994)

9. Reconnection Event Nagai et al. (1998) Highly Energetic Event

10. Near the Equatorial Plane Ions Convection Flows V > 2500 km/s Electrons Peak is shifted tailward Nagai et al. (1998) 1404:59 UT January 27, 1996

11. Off the Equtorial Plane Ions Inflowing Ions (convection) Field-Aligned Flows Electrons Strongly Accelerated Nagai et al. (1998) 1404:34 UT January 27, 1996

12. Structure of Magnetic Reconnection TypeB TypeN Ions Electrons Nagai et al. (1998)

13. Outer Boundary Region in Tailward Flows Ions Inflowing Ions Tailward Field-Aligned Flows Electrons Inflowing Electrons Tailward Escaping Electrons Nagai et al. (1998) 1406:12 UT January 27, 1996

14. OuterBoundary Region For Earthward Flows Ions Earthward Field-Aligned Flows Electrons Inflowing Electrons Earthward Escaping Electrons Nagai et al. (1998) 1335:35 UT February 18, 1996

15. Structure of Magnetic Reconnection TypeB TypeA TypeN Ions Electrons a part of the Hall current system Nagai et al. (1998)

17. The Hall Current System • Structure of the current system • Current carrier • Current density • Effect in the magnetic field By

18. The Hall current system Ion-Electron Decoupling B. U. O. Sonnerup (1979)

19. Hybrid simulation for reconnection Vex M.S. Nakamura et al. (1998)

20. Reconnection event Nagai et al. (2001)

21. Electrons for Hall currents in the December 10, 1996, event Nagai et al. (2001)

22. Particle simulation for reconnection Hoshino (1998)

23. 2 Hall Current density ・・・・ 6～13 ｎＡ/m Nagai et al. (2001)

24. Examples of the Hall currents’ Electrons Earth Earth Tail Tail 1119:32 UT August 3,1996 Earthward Flow at XGSM = -10.20 Fujimoto et al. (2001) 1347:19 UT January 10,1995 Tailward Flow at XGSM = -46.34 Fujimoto et al. (1997)

25. By Effect by the Hall current system By < 0 By > 0 Nakabayashi and Machida (1997) Hoshino (2001)

26. By Effect in the Hall current system The most outer region - + + - Nagai et al. (2001)

27. Unsolved Questions With Geotail or with Future Missions • Source of anomalous resistivity • Ion dynamics near the diffusion region • Electron dynamics near the diffusion region • Large By magnetic field with large Bz

28. Source of Anomalous Resistivity Lower Hybrid Waves ? Shinohara et al. (1998)

29. Complex Ion Distributions Ion Dawn Dusk Electron February 19, 2001 1523:02 UT

30. Ion Electron Dusk Dawn Anomalous Electron Distributions February 10, 2000 1825:59 UT

31. Large By in Earthward Flows Bz>0 Bz<0

32. Large negative Bz 1 sec

33. Future Mission • SCOPE (Scale Coupling in Plasma Environment) • High time resolution in particle observations • Full energy coverage in particle observations • Multi-point observations to know the s/c location • relative to the neutral line