HR: 16:30h
AN: SM34A-03    [Abstracts]
TI: Consequences of Ion Shell Instabilities in the Plasma Sheet Boundary Layer
AU: * Ashour-Abdalla, M
EM: mabdalla@igpp.ucla.edu
AF: Department of Physics and Astronomy, University of California , Los Angeles, CA 90095-1547 United States
AU: * Ashour-Abdalla, M
EM: mabdalla@igpp.ucla.edu
AF: Institute of Geophysics and Planetary Physics, University of California, Los Angeles, CA 90095-1567 United States
AU: Leboeuf, J
EM: leboeuf@physics.ucla.edu
AF: Department of Physics and Astronomy, University of California , Los Angeles, CA 90095-1547 United States
AU: Schriver, D
EM: dave@igpp.ucla.edu
AF: Institute of Geophysics and Planetary Physics, University of California, Los Angeles, CA 90095-1567 United States
AU: Bosqued, J
EM: bosqued@cesr.fr
AF: CESR/CNRS, 9 Ave Colonel-Roche , Toulouse, CDX 31028 France
AU: Cornilleau-Werhlin, N
EM: nicole.cornilleau@cetp.ipsl.fr
AF: CETP/CNRS/UVSQ, 10-12 Ave de Europe, Velizy, 78140 France
AU: Sotnikov, V I
EM: sotnikov@physics.unr.edu
AF: Department of Physics, University of Nevada, Reno, NV 89557 United States
AU: Marchaudon, A
EM: am@mssl.ucl.ac.uk
AF: Mullard Space Science Laboratory, University College London, Surrey, RH5 6NT United Kingdom
AU: Fazakerley, A N
EM: anf@mssl.ucl.ac.uk
AF: Mullard Space Science Laboratory, University College London, Surrey, RH5 6NT United Kingdom
AB: Recent Cluster satellite observations made in the Earth's plasma sheet boundary layer (PSBL) region have shown the presence of ion shell distribution functions coincident with broadband electrostatic waves. The shell distribution functions take the form of ions with about the same drift speed isotropically distributed in velocity space on a sphere and are related to velocity dispersed ion structures (VDIS) in the near-Earth PSBL. We have examined ion shell instabilities in the presence of a cold ion and electron background using a magnetized two-and-one-half-dimensional electrostatic particle in cell code with full dynamics ions and guiding center electrons with full parallel dynamics. Results from the numerical simulations indicate that a series of ion Bernstein modes are preferentially excited transverse to the ambient magnetic field, along with a lower level of wave power at oblique angles. The cold background ions are heated in both the parallel and transverse directions accompanied by electron energy gain parallel to the ambient magnetic field. The preferential transverse energization of the cold background ions is due to a linear non-stochastic ion cyclotron heating mechanism and overall saturation of the instability occurs due to thermalization of the shell combined with the cold background ion heating. Comparison with Cluster observations shows that the observed electrostatic wave spectrum from a few Hz up to several hundred Hz is in good agreement with that expected from the shell instability. Also the cold background ions show a temperature anisotropy with T_⊥ > T_∥, in qualitative agreement with that expected from the saturation of the shell instability. Finally Cluster electron observations show evidence of heating parallel to the magnetic field. We are in the process of examining electromagnetic aspects of the instability driven by the observed ion shell distribution.
DE: 7827 Kinetic and MHD theory
DE: 7829 Kinetic waves and instabilities
DE: 7846 Plasma energization
DE: 7867 Wave/particle interactions (2483, 6984)
SC: SPA-Magnetospheric Physics [SM]
MN: Fall Meeting 2005