HR: 09:45h
AN: NG21A-08    [Abstracts]
TI: Observational Evidence for Nonlinear Charged Particle Dynamics in the Magnetotail.
AU: * Ansher, J A
EM: ansher@phy.ilstu.edu
AF: Illinois State University, Department of Physics, Normal, IL 61790-4560 United States
AU: Holland, D L
EM: holland@phy.ilstu.edu
AF: Illinois State University, Department of Physics, Normal, IL 61790-4560 United States
AU: Martin, R F
EM: rfm@phy.ilstu.edu
AF: Illinois State University, Department of Physics, Normal, IL 61790-4560 United States
AU: Matsuoka, H
EM: hmb@phy.ilstu.edu
AF: Illinois State University, Department of Physics, Normal, IL 61790-4560 United States
AB: Computer simulations of nonlinear charged particle dynamics in magnetotail-like magnetic fields have pointed towards the existence of a phase space resonance effect that manifests itself in the preferential forward or back scattering as a function of the energy of incoming particles as they interact with the current sheet. This resonance has been shown to manifest itself as a series of peaks in the ion distribution function where the separation of the peaks is proportional to the fourth root of the normalized particle energy. The normalization in turn depends on parameters that describe the magnetic field structure, i.e. the current sheet half-thickness and the ratio of the magnetic field strength at the midplane, $B_z$, to the magnetic field strength far from the field reversal but still in the plasma sheet, $B_0$. In this paper we will examine the underlying physics of the current sheet as a chaotic scattering system and demonstrate how the energy resonance signature in the ion distribution function may be used to determine the current sheet structure. We also present the results of a survey of the current sheet structure as determined using the energy resonance signature in the region from 20 to 100 earth radii downtail.
DE: 7839 Nonlinear phenomena
DE: 2744 Magnetotail
DE: 2764 Plasma sheet
DE: 2794 Instruments and techniques
DE: 3220 Nonlinear dynamics
SC: Nonlinear Geophysics [NG]
MN: 2004 AGU Fall Meeting