relationship of plasma sheet and plasma sheet boundary layer to auroras
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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 - PowerPoint PPT PresentationTRANSCRIPT
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 SheetGringauz et al., Soviet Astron, AJ 4, 680, 1961
Anderson, K., JGR 70, 4741, 1965Bame et al, JGR, 72, 113, 1967Frank, L., JGR. 72, 185, 1967
Plasma Sheet Boundary LayerFrank, L., Phys. Sol. Plan. Environ., 2, Eds. D. Williams, AGU, 1967
DeCoster and Frank, JGR, 84, 5009, 1979Forbes et al., GRL, 8, 261, 1981Eastman et al., JGR., 89, 1553, 1984Takahashi and Hones, JGR 93, 8558, 1988.M. Nakamura et al., JGR, 96, 5631, 1991
A Schematic diagram of boundary layers(Eastman et al., JGR 90, 9541, 1985)
Based on ion measurements
Connection to Electron Precipitation and Aurora
J. Heppner et al., JGR 72, 5417, 1967
E. Hones et al., JGR 73, 1968
G. Parks and J. Winckler, JGR 73, 5786,1968
J. Hargreaves et al., Proc. Int. Symp. On Sol-Terr. Phys., San Paolo, Brazil, 1974
J. A. Sauvaud et al., JGR 92, 2365, 1987
Parks and Winckler (1968)
ATS-1 Energetic Electrons
ATS-1 magnetic field
College magnetogram
ATS-1 Energetic Electrons
Bremsstrahlung X-rays
Substorm behavior at synchronous altitude and plasma sheet(Sauvaud et al., 1987)
Large <v> in ions at CPS/PSBL
Bursty bulk flow of ions in CPS
Large <v> in ions observed in PSBL
Bursty Bulk Flows interpreted in terms of a tail merging model
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>?
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
Field-aligned beams in PSBL
Moments of the df and B
Pitch-angle spectrogram
Examples of High <v> events (BBF) (March 27, 1996 studied by Angelopoulos et al., 1997)
Conjunction event with UVI(July 29, 1996 event studied by Fillingim et al., 27, 1379, 2000)
Relationship of pseudo breakup and substorm expansion
Pi-2 near footprint of WIND
Pseudo breakups and substorm expansion in PS and PSBL
Distribution Function and Energy Spectra
High time resolution plots during pseudo breakups
What we learned about pseudobreakups and substorms
Cluster current sheet crossings on October 1, 2001 (Runov et al., 2003)
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)
Examples of Distribution function(Wilber et al., 2004)
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
Remote Sensing Effects
Thick current sheet
Thin current sheet
model
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.
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?
The End