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Ann. Geophys., 20, 1559-1575, 2002
www.ann-geophys.net/20/1559/2002/
© European Geosciences Union 2002
Origin of some anisotropic tailward flows in the plasma sheet
J. A. Wanliss1,*, R. D. Sydora1, G. Rostoker1, and R. Rankin1
1University of Alberta, Department of Physics, Edmonton, Alberta, T6G 2J1, Canada
*now at: Embry-Riddle Aeronautical University, Physical Sciences Dept., Daytona Beach, Fla. 32114, USA
Correspondence to: J. A. Wanliss
(james.wanliss@erau.edu)
Abstract. We use a test particle model to explore
anisotropy and fast flows in the central plasma sheet (CPS) that are a
consequence of plasma sheet boundary layer (PSBL) ion beam dynamics. Ion
distributions and flows (velocity moments) in the CPS and equatorial current
sheet (CS) are compared and we find that mirroring of initially earthward beams
from the PSBL, and their subsequent convection to the CS region, results in
strong anisotropy throughout the CPS. At higher latitudes, velocity moments are
field-aligned and feature earthward flow. Deeper in the CPS, velocity moments
yield flows in the anti-earthward direction. There is no clear distinction
between the PSBL and CPS, since velocity distributions with large streaming
components occur throughout the model CPS, but in the CS region they are
anisotropic and nongyrotropic. In the CS region velocity moments can feature
anti-earthward cross field flows. These tailward flows (> 400 km/s) are
observed in the CS region between X = - 20 to - 30 RE
due to nonadiabatic effects. Model results suggest that fast tailward plasma
flows can be obtained without necessarily appealing to magnetotail processes
associated with dynamic geomagnetic activity.
Key words. Magnetospheric physics (magnetospheric
con-figuration and dynamics) – Space plasma physics (charge particle motion
and acceleration; numerical simulation studies)
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