HR: 08:30h
AN: SM31E-03 INVITED    [Abstracts]
TI: Testing the necessity of transient spikes in the drivers for creating a storm-time ring current
AU: * Liemohn, M W
EM: liemohn@umich.edu
AF: University of Michigan, 2455 Hayward St., Ann Arbor, MI 48109, United States
AU: Ilie, R
EM: rilie@umich.edu
AF: University of Michigan, 2455 Hayward St., Ann Arbor, MI 48109, United States
AU: Ridley, A J
EM: ridley@umich.edu
AF: University of Michigan, 2455 Hayward St., Ann Arbor, MI 48109, United States
AU: Kozyra, J U
EM: jukozyra@umich.edu
AF: University of Michigan, 2455 Hayward St., Ann Arbor, MI 48109, United States
AU: Thomsen, M F
EM: mthomsen@lanl.gov
AF: Los Alamos National Laboratory, ISR-1, MS D466, Los Alamos, NM 87545, United States
AU: Borovsky, J E
EM: jborovsky@lanl.gov
AF: Los Alamos National Laboratory, ISR-1, MS D466, Los Alamos, NM 87545, United States
AB: The role of transient spikes in upstream solar wind parameters and near-Earth plasma sheet parameters is investigated through a series of numerical simulations. During magnetic storms, the near-Earth plasma sheet density (as observed at geosynchronous altitude) is often enhanced relative to its normal, quiescent level. In addition to a baseline increase of the density of up to a few per cubic centimeter lasting several hours, there are usually short-lived (a few to tens of minutes) increases on top of this (up to double the baseline). In addition, the solar wind parameters also often have numerous short-lived spikes and fluctuations within it. The question then arises of the relative contribution of these transient spikes in the drivers to the storm-time ring current intensity. To address this issue, a series of simulations are conducted using the Hot Electron and Ion Drift Integrator (HEIDI) model (formerly the Michigan version of RAM). Various running averages of the upstream solar wind conditions and geosynchronous orbit nightside boundary conditions are used to drive HEIDI. It is found that the spikes are simply adding a linear contribution to the ring current intensity over the baseline (averaged) input levels, and that any nonlinear influences occur beyond the HEIDI simulation domain (i.e., at high latitudes or in the tail). That is, the spikes do not last long enough to develop nonlinear influences on the ring current's total energy content. The HEIDI results are compared against global magnetospheric modeling results using averaged input parameters into the Space Weather Modeling Framework (SWMF), which show a nonlinear response to transient spikes.
DE: 2753 Numerical modeling
DE: 2764 Plasma sheet
DE: 2778 Ring current
DE: 2784 Solar wind/magnetosphere interactions
DE: 2788 Magnetic storms and substorms (7954)
SC: SPA-Magnetospheric Physics [SM]
MN: 2007 Fall Meeting