HR: 1340h
AN: SM33A-1112    [Abstracts]
TI: Magnetospheric ULF Oscillations Driven by Interior Kelvin-Helmholtz Modes
AU: * Claudepierre, S
AF: University of Colorado - LASP, 1234 Innovation Drive, Boulder, CO 80303, United States
AU: Elkington, S
AF: University of Colorado - LASP, 1234 Innovation Drive, Boulder, CO 80303, United States
AU: Wiltberger, M
AF: NCAR - HAO, 3450 Mitchel Lane, Boulder, CO 80301, United States
AB: Observations of field line resonances in the magnetosphere are characterized by a discrete set of ULF band frequencies. Determining the magnetospheric process that is responsible for this discrete set of frequencies has received much attention in the literature. The Kelvin-Helmholtz instability at the magnetopause boundary has been suggested as a possible candidate but it can only account for at most two discrete frequencies. Cavity mode oscillations have also been proposed but the geometric assumptions that must be made cannot account for the lowest frequency observations. In addition, cavity mode oscillations are seldom seen in magnetospheric observations. We present results from global magnetohydrodynamic (MHD) simulations of the solar wind/magnetosphere interaction that suggest the generation of interior Kelvin-Helmholtz (KH) modes inside the magnetosphere. These KH modes are generated locally, in the post dusk and pre dawn sectors of the magnetosphere. They arise as a result of counterstreaming sunward and tailward flows during periods of strong magnetospheric convection. We demonstrate how these interior KH modes can drive strong ULF oscillations inside the magnetosphere. A feature of these driven ULF oscillations is a discrete set of ULF band frequencies, a common feature of field line resonance observations.
DE: 2730 Magnetosphere: inner
DE: 2740 Magnetospheric configuration and dynamics
DE: 7836 MHD waves and instabilities (2149, 2752, 6050)
SC: SPA-Magnetospheric Physics [SM]
MN: 2007 Fall Meeting