HR: 0800h
AN: SM31B-1229    [Abstracts]
TI: The specific entropy of the plasma sheet as a controlling factor for the injection of a storm-time ring current
AU: * Lemon, C L
EM: colby@rice.edu
AF: Rice University, 6100 Main St./MS108, Houston, TX 77005 United States
AU: Wolf, R A
EM: rawolf@rice.edu
AF: Rice University, 6100 Main St./MS108, Houston, TX 77005 United States
AU: Hill, T W
EM: hill@rice.edu
AF: Rice University, 6100 Main St./MS108, Houston, TX 77005 United States
AU: Sazykin, S
EM: sazykin@rice.edu
AF: Rice University, 6100 Main St./MS108, Houston, TX 77005 United States
AU: Spiro, R W
EM: spiro@rice.edu
AF: Rice University, 6100 Main St./MS108, Houston, TX 77005 United States
AU: Toffoletto, F R
EM: toffo@rice.edu
AF: Rice University, 6100 Main St./MS108, Houston, TX 77005 United States
AU: Birn, J
EM: jbirn@lanl.gov
AF: Los Alamos National Laboratory, MS D466, Los Alamos, NM 87545 United States
AU: Hesse, M
EM: michael.hesse@nasa.gov
AF: NASA/Goddard Space Flight Center, Code 696, Greenbelt, MD 20771 United States
AB: Simulation results are presented which explore the importance of the inner plasma sheet specific entropy ($pV^{5/3}$, where p is pressure and $V = \int ds/B$ is the flux tube volume) for controlling the strength and depth of ring current particle injections during magnetic storms. The simulation model is the RCM--E (Rice Convection Model -- Equilibrium), which calculates the energy-dependent magnetic and electric drifts of particles within self-consistently computed magnetic and electric fields. The results demonstrate that inner plasma sheet reductions in the specific entropy can drive region 1 Birkeland currents that enhance the westward electric field in the depletion region; the strong electric field then propels plasma earthward, into the ring current. In contrast, earthward convection of heavily loaded (insufficiently depleted) plasma sheet flux tubes is impeded by the immense pressure gradient that would result from squeezing that much plasma into the much smaller volume of a ring current flux tube. In other words, insufficient depletion disallows the flux tubes from taking on the quasi-dioplar shape necessary to penetrate into the ring current. Flux tube content reductions are observed during the substorm expansion phase, suggesting one potential process (though perhaps not the only one) that could lead to ring current injection. The ability of the plasma sheet specific entropy to influence the injection of ring current particles, and the implications for understanding the differences between SMC and Sawtooth events will be examined.
DE: 7843 Numerical simulation studies
DE: 2736 Magnetosphere/ionosphere interactions
DE: 2764 Plasma sheet
DE: 2778 Ring current
DE: 2788 Storms and substorms
SC: SPA-Magnetospheric Physics [SM]
MN: 2004 AGU Fall Meeting