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Relationship of Plasma Sheet and Plasma Sheet Boundary Layer to Auroras

Relationship of Plasma Sheet and Plasma Sheet Boundary Layer to Auroras. George K. Parks Space Sciences Laboratory University of California, Berkeley, CA 94720 • Review • Discuss Recent Observations • Summary. Early Observations. Central Plasma Sheet

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Relationship of Plasma Sheet and Plasma Sheet Boundary Layer to Auroras

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  1. Relationship of Plasma Sheet and Plasma Sheet Boundary Layer to Auroras George K. Parks Space Sciences Laboratory University of California, Berkeley, CA 94720 • Review • Discuss Recent Observations • Summary

  2. Early Observations Central Plasma Sheet Gringauz et al., Soviet Astron, AJ 4, 680, 1961 Anderson, K., JGR70, 4741, 1965 Bame et al, JGR, 72, 113, 1967 Frank, L., JGR. 72, 185, 1967 Plasma Sheet Boundary Layer Frank, L., Phys. Sol. Plan. Environ., 2, Eds. D. Williams, AGU, 1967 DeCoster and Frank, JGR, 84, 5009, 1979 Forbes et al., GRL, 8, 261, 1981 Eastman et al., JGR., 89, 1553, 1984 Takahashi and Hones, JGR 93, 8558, 1988. M. Nakamura et al., JGR, 96, 5631, 1991

  3. A Schematic diagram of boundary layers(Eastman et al., JGR 90, 9541, 1985) Based on ion measurements

  4. Connection to Electron Precipitation and Aurora J. Heppner et al., JGR 72, 5417, 1967 E. Hones et al., JGR73, 1968 G. Parks and J. Winckler, JGR73, 5786,1968 J. Hargreaves et al., Proc. Int. Symp. On Sol-Terr. Phys., San Paolo, Brazil, 1974 J. A. Sauvaud et al., JGR92, 2365, 1987

  5. Parks and Winckler (1968) ATS-1 Energetic Electrons ATS-1 magnetic field College magnetogram ATS-1 Energetic Electrons Bremsstrahlung X-rays

  6. Substorm behavior at synchronous altitude and plasma sheet(Sauvaud et al., 1987)

  7. Large <v> in ions at CPS/PSBL Large <v> in ions observed in PSBL Bursty bulk flow of ions in CPS Bursty Bulk Flows interpreted in terms of a tail merging model

  8. Some questions about the large ion <v> events Are bursty bulk flows really ExB flows in CPS? What phase space features are responsible for the large ion <v>?

  9. Definitions Particle Measurements come from Electrostatic analyzers and Solid State Detectors Bulk Plasma Parameters (Computed quantities) < n > =  f(r, v; t) d3v < v > =  v f (r, v; t) d3v < v2> =  (vi - <v>)(vj - <v>) f (r, v) d3v Working Definition of CPS (Angelopoulos et al., 1992) Bxy < 15 nT, Bx/Bxy > 0.5

  10. Field-aligned beams in PSBL Moments of the df and B Pitch-angle spectrogram

  11. Examples of High <v> events (BBF) (March 27, 1996studied byAngelopoulos et al., 1997)

  12. Conjunction event with UVI(July 29, 1996event studied by Fillingim et al., 27, 1379, 2000)

  13. Relationship of pseudo breakup and substorm expansion

  14. Pi-2 near footprint of WIND

  15. Pseudo breakups and substorm expansion in PS and PSBL

  16. Distribution Function and Energy Spectra

  17. High time resolution plots during pseudo breakups

  18. What we learned about pseudobreakups and substorms

  19. Cluster current sheet crossings on October 1, 2001 (Runov et al., 2003)

  20. Thin Current Sheet During periods of strong geomagnetic activity, the current sheet can thin to ion gyroradius scales (Mitchell et al., 1990). Particles can gain energy by nonadiabatic motions allowing traversal across tail electric field (Speiser orbits). Strong gradients can lead to nongytropic ion distributions due to “remote sensing” effects (Williams, 1980; Marcucci et al., 2004) which have been used to estimate magnetotail motions and plasma sheet orientations (Owens et al.,1995). Ampte observations of nongytropic magnetotail ions were interpreted as signatures of gyrophase bunching (Nakamura et al., 1991). Geotail observed nongytropic ion distributions intepreted them as a mixture of different sources and acceleration histories (Mukai et al., 1998)

  21. Examples of Distribution function(Wilber et al., 2004)

  22. Test particle simulation(Lee et al., GRL 31, Dec 2004) Harris current sheet Bx = Botanh (z/L) N = No/cosh2 (z/L) Initial condition: Maxwellian distribution with T cutoff at 0.75 Vti (observed) z/L position wrt current sheet i/L kinetic effects with finite Larmor radii effect

  23. Remote Sensing Effects Thick current sheet model Thin current sheet

  24. Summary High <v> does not mean the plasma is flowing. High <v> can result near thin boundaries because of remote sensing effects. High <v> does not mean the plasma is flowing. Even stationary plasma can yield high <v> because of finite gyroradius effects. It is important to examine the phase space distribution before concluding there is high speed flows because <v> is large.

  25. Many problems still to be studied. Origin of the beams in the PSBL? Distinguish observationally whether a substorm is due to onset of a tearing mode instability or current disruption (ballooning mode)? Role of electrons in the overall dynamics? Requirements for the plasma and particle instruments to resolve some of the observational issues?

  26. The End

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