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Magnetic reconnection in the magnetotail: Geotail observations

World Space Environment Forum 2005 May 4, 2005 Wednesday 09:00 – 09:20 AM. Magnetic reconnection in the magnetotail: Geotail observations. T. Nagai Tokyo Institute of Technology. Geotail. distant tail. near tail. Geotail Near-Tail Observations

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Magnetic reconnection in the magnetotail: Geotail observations

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  1. World Space Environment Forum 2005 May 4, 2005 Wednesday 09:00 – 09:20 AM Magnetic reconnection in the magnetotail: Geotail observations T. Nagai Tokyo Institute of Technology

  2. Geotail distant tail near tail

  3. Geotail Near-Tail Observations 10 x 31 RE orbits Solar Wind Bow Shock Magetosheath Magnetopause Plasma Sheet

  4. High-Speed Tailward Flowing Ions High Accelerated Electrons Ion Electron V=3000km/s Outflow Ions Convection Inflow Ions Outflow Ions Nagai et al. (JGR 1998)

  5. 1406:12 UT January 27, 1996 Outer Boundary Region in Tailward Flows Ions Inflowing Ions Tailward Field-Aligned Flows Electrons Inflowing Electrons Tailward Escaping Electrons Hall Currents in Magnetic Reconnection Nagai et al. (1998)

  6. December 10, 1996

  7. 2 Hall Current density ・・・・ 6～13 nA/m Electrons for Hall currents in the December 10, 1996, event Nagai et al. (JGR 2001)

  8. In Situ Observations of Magnetic Reconnection in 1995 - 1997

  9. Solar wind control of the radial distance of • the magnetic reconnection site in the magnetotail • T. Nagai and M. Fujimoto (Tokyo Institute of Technology) • R. Nakamura and W. Baumjohann (OEAW) • A. Ieda (Solar-Terrestrial Environment Laboratory) • I. Shinohara (ISAS) • S. Machida (Kyoto University) • Y. Saito and T. Mukai (ISAS)

  10. Solar Maximum High B and High V Solar Minimum Low B and Low V Solar Wind IMF Bt Velocity In 1995-1997

  11. Geotail Near-Tail Observations 10 x 31 RE orbits Plasma Sheet (β> 1) XGSM = -10 to -31 RE and YGSM = -5 to +10 RE

  12. Solar Minimum Solar Maximum in 1996-1998 in 1999-2003 Even Coverage of XGSM = -10 to -31 RE

  13. 1996/02/18 Reconnection Event magnetic field fast tailward flows with Bz < 0 electron energy spectra flux thermal accelerated highly accelerated electrons energy

  14. Solar Minimum Solar Maximum in 1996-1998 in 1999-2003 XGSM = -17 to -31 RE XGSM = -25 to -31 RE

  15. Average Solar Wind Parameters Prior to Each Reconnection Event Total 34 Events SW parameters during 60 minutes prior to each reconnection event

  16. Solar Wind Velocity ? circles 1996-1998 events black dots 1999-2003 events

  17. Solar Wind Dynamic Pressure ?

  18. Southward IMF Bz

  19. Southward IMF Bz circles 1996-1998 events black dots 1999-2003 events X = -25 RE

  20. Solar Wind Energy Input

  21. Solar Wind Energy Input Midtail Near-Tail X = -25 RE

  22. Average solar wind parameters for the period from -6 to +2 hours 9 events 25 events Near-tail Midtail Reconnection Start Time

  23. Solar Wind Energy Input Near-tail Midtail

  24. Accumulation of Solar Wind Energy Input Near-Tail Midtail

  25. Solar Wind Velocity Near-Tail Midtail High Velocity 520 km/s Low velocty 460 km/s

  26. Solar Wind Dynamic Pressure Near-Tail Midtail 2 nPa high velocity and low density 2 nPa low velocity and high density

  27. Accumulation of Solar Wind Energy Input Near-Tail Midtail Solar Wind Input Energy x 2

  28. Solar Wind Energy Input High Efficiency of Solar Wind Energy Input Near-Tail Low Efficiency of Solar Wind Energy Input Midtail

  29. High Efficiency of Solar Wind Energy Input Near-Tail Low Efficiency of Solar Wind Energy Input Midtail

  30. 1. Reconnection event analysis 34 events • Tailward flow with Bz < 0 • Electron acceleration • Tailward flow event analysis 174 events • Tailward flow with Bz < 0 • No electron acceleration • Cluster events at 15-19 RE (from Nakamura et al., GRL 2004)

  31. IMF Bz 15 tailward flows 56 tailward flows 118 tailward flows Cluster Near-tail Midtail

  32. Solar Wind Energy Input Cluster Near-tail Midtail

  33. Accumulation of Solar Wind Energy Input Cluster Near-tail Midtail

  34. Past Spacecraft Observations Vela 1967-1968 Hones et al., 1971; 1973 IMP 6 1971-1973 Hones and Schindler, 1979 ISEE-1 1980 Cattell and Mozer, 1984 ISEE-2 1978-1979 Angelopoulos et al. 1994 CDAW-6 McPherron and Manka, 1985 IRM 1985-1986 Baumjohann et al., 1988,1989,1990,1991 Geotail 1996-1998 Nagai et al. 1998 1999-2003 This study Cluster 2001-2002 Nakamura et al., 2004

  35. Past Spacecraft Observations Vela 1967-1968 Hones et al., 1971; 1973 at 18 RE Nishida and Nagayama (1973) …somewhere between X = -10 RE to -25 RE 15-18 RE

  36. Past Spacecraft Observations ISEE-1 1980 Cattell and Mozer, 1984 ISEE-2 1978-1979 Angelopoulos et al. 1994 CDAW-6 McPherron and Manka, 1985 IRM 1985-1986 Baumjohann et al., 1988,1989,1990,1991 CDAW-6 13-14 RE Earthward Flows inside 20 RE

  37. VELA 15RE IMP-6 ISEE-2 > 22RE ISEE-1 > 21 RE IRM > 18 RE Geotail 1996-1998 > 25 RE Geotail 1999- Cluster 15-30RE

  38. Conclusions • Reconnection takes place in the near-Earth tail (midtail) • under the high (low) solar wind energy input. • Controlling factor is efficiency of solar wind input energy, • not the total amount of input energy. • Tail reconnection site can be controlled • by solar cycle variations in the solar wind.

  39. 1996 1999 2002 1997 2000 2003 1998 2001 2004

  40. High Efficiency of Low Efficiency of Solar Wind Energy Input Solar Wind Energy Input Near-Tail Midtail XGSM = -15 to -25 RE XGSM = -25 to -30 RE

  41. VELA 15RE IMP-6 ISEE-2 > 22RE ISEE-1 > 21 RE IRM > 18 RE Geotail 1996-1998 > 25 RE Geotail 1999- Cluster 15-30RE

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

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