HR: 17:15h
AN: SM22D-06    [PDF]
TI: Firehose instability near substorm expansion-phase onset?
AU: Ji, S
EM: jishuo@rice.edu
AF: Physics and Astronomy Dept., Rice University, MS108, P. O. Box 1892, Houston, TX 77251 United States
AU: * Wolf, R A
EM: rawolf@rice.edu
AF: Physics and Astronomy Dept., Rice University, MS108, P. O. Box 1892, Houston, TX 77251 United States
AB: The evolution of plasma ejected earthward from a patch of reconnection at about 25 RE is studied using a double-adiabatic-MHD simulation of a thin filament. Firehose instability occurs in the simulation after a compressional shock reflects from the near-Earth region. The tailward-propagating compressional wave, which brakes the earthward flow in the filament, is thus characterized by strong magnetic fluctuations. Within the context of the Near-Earth-Neutral-Line model of substorms, we suggest that firehose instability might cause the intense magnetic-field fluctuations that are observed in the inner plasma sheet at substorm onset. To assess the accuracy of double-adiabatic MHD, we tested it for a situation that resembles the substorm-generated filament but is simple enough to allow an exact kinetic theory solution. The test confirms that double-adiabatic MHD does a reasonable job of predicting when the firehose criterion is satisfied.
DE: 2740 Magnetospheric configuration and dynamics
DE: 2744 Magnetotail
DE: 2753 Numerical modeling
DE: 2764 Plasma sheet
DE: 2788 Storms and substorms
SC: SPA - Magnetospheric Physics [SM]
MN: 2003 Fall Meeting