HR: 12:05h
AN: SM12B-08    [Abstracts]
TI: Effects of Magnetospheric Activity on the Current Sheet Energy Resonance Ion Distribution Function Signature
AU: * Bush, C J
EM: cbush@phy.ilstu.edu
AF: Illinois State University Department of Physics, 313C Moulton Hall, Normal, IL 61790-4560, United States
AU: Holland, D L
EM: holland@phy.ilstu.edu
AF: Illinois State University Department of Physics, 313C Moulton Hall, Normal, IL 61790-4560, United States
AB: Theory and simulations of nonlinear charged particle dynamics in current sheet -like magnetic fields have predicted a signature of the dynamics that manifests itself a series of peaks in the ion distribution function. The separation of the peaks has been shown to scale as a combination of the fourth root of the ion energy and parameters that describe the current sheet topology, i.e. the current sheet scale length, and the ratio of the magnetic field strength at the mid-plane to the asymptotic magnetic field strength. This signature has been observed during quiet times (Kp<1+) in both the AMPTEE and Geotail Data sets. In this paper, we examine the effects of magnetopsheric activity (as measured by Kp) on the particle signature as measured by the Geotail satellite in the region 20-25 earth radii downtail. We show that the signature is easily observed for Kp < 4- and that as a general rule, the larger the value of Kp, the closer the peaks are together. For larger values of Kp we find that whereas there is some indication of peaks in the ion distributions, the separations do not have the same scaling and are often completely smeared out. We have also used the peaks in the distribution function coupled with magnetic field measurements to determine the current sheet thickness. As would be anticipated, the sheet is thinner for higher levels of magnetospheric activity.
DE: 2744 Magnetotail
DE: 2764 Plasma sheet
DE: 7805 Chaos (4420)
DE: 7807 Charged particle motion and acceleration
DE: 7839 Nonlinear phenomena (4400, 6944)
SC: SPA-Magnetospheric Physics [SM]
MN: 2007 Fall Meeting