HR: 17:45h
AN: SM22D-08    [PDF]
TI: Substorm Injection Modeling With Non-dipolar, Time-dependent Background Field
AU: * Zaharia, S
EM: szaharia@lanl.gov
AF: Los Alamos National Laboratory, NIS-1, MS D466, Los Alamos, NM 87545 United States
AU: Birn, J
EM: jbirn@lanl.gov
AF: Los Alamos National Laboratory, NIS-1, MS D466, Los Alamos, NM 87545 United States
AU: Reeves, G
EM: gdreeves@lanl.gov
AF: Los Alamos National Laboratory, NIS-1, MS D466, Los Alamos, NM 87545 United States
AU: Thomsen, M
EM: mthomsen@lanl.gov
AF: Los Alamos National Laboratory, NIS-1, MS D466, Los Alamos, NM 87545 United States
AU: Cheng, C
EM: fcheng@pppl.gov
AF: Princeton Plasma Physics Laboratory, Princeton University, P.O. Box 451, Princeton, NJ 08543 United States
AB: We model substorm energetic particle injections by studying the interaction of particles with earthward-propagating electromagnetic pulses of westward electric field and consistent magnetic field with localized radial and azimuthal extents, superposed over a background magnetic field. The improvement in the current work over previous models is the consideration of a non-dipolar background magnetic field before the pulse arrives (corresponding to the stretched field during the substorm growth phase), which changes in a time-dependent manner and transforms into a dipole field in the wake of the pulse. The particle motion is still adiabatic, even in the lower stretched field, and therefore both ions and electrons are dragged earthward by the ExB drift to regions of higher magnetic field, thus undergoing betatron acceleration. As in the previous model, we obtain fully-analytical solutions for the particle motion. We present an analysis of the differences in the results with the current model vs. the previous model (with dipole background), both for the particle orbits and the injected particle fluxes. We also discuss the dependence of the ion and electron injections on pulse parameters, such as speed, field magnitude and spatial extent. The results with the non-dipolar, time-dependent background field show marginal increase in injection strength for energies of 10 to 400 keVs and typical pulse parameters compared to the case of dipole background, however the differences become more significant for very active events or very high particle energies.
DE: 2712 Electric fields (2411)
DE: 2720 Energetic particles, trapped
DE: 2730 Magnetosphere--inner
DE: 2788 Storms and substorms
DE: 7807 Charged particle motion and acceleration
SC: SPA - Magnetospheric Physics [SM]
MN: 2003 Fall Meeting