HR: 11:35h
AN: SM51E-06    [PDF]
TI: Characterization of the global {ULF} environment during the 09/24/1998 geomagnetic storm, and effect on energetic electron dynamics.
AU: * Elkington, S R
EM: scot.elkington@lasp.colorado.edu
AF: LASP, University of Colorado, 1234 Innovation Drive, Boulder, CO 80303 United States
AU: Chan, A A
EM: aac@landau.rice.edu
AF: Rice University, Department of Physics and Astronomy, 6100 Main Street, Houston, TX 77005 United States
AU: Fei, Y
EM: yfei@rice.edu
AF: Rice University, Department of Physics and Astronomy, 6100 Main Street, Houston, TX 77005 United States
AU: Wiltberger, M J
EM: wiltbemj@hao.ucar.edu
AF: NCAR/HAO, 3450 Mitchel Lane, Boulder, CO 80301 United States
AU: Baker, D N
EM: dan.baker@lasp.colorado.edu
AF: LASP, University of Colorado, 1234 Innovation Drive, Boulder, CO 80303 United States
AU: Hudson, M K
EM: maryk@gaia.dartmouth.edu
AF: Dartmouth College, HB6127, Hanover, NH 03755 United States
AB: The dynamics of energetic particle populations in the inner magnetosphere can be quantitatively described by a Fokker-Planck equation written in terms of the invariant quantities {\it M}, {\it K}, and {\it L}. In particular, ULF waves, with frequencies in the range $\sim$1-10~mHz, can lead to efficient diffusive transport in the radial coordinate corresponding to the third invariant, {\it L}. The appropriate transport coefficient, $D_{LL}$, depends not only on the frequency spectrum and power of the waves involved, but also on the global mode structure of the waves as well as the large scale magnetospheric configuration, i.e. the state of magnetospheric compression and stretching due to the effect of the solar wind dynamic pressure and magnetospheric current systems. In this work, we use MHD simulations to model the ULF wave activity occurring during the geomagnetic storm of September 24-26, 1998, and analyze the wave activity both in terms of temporal and frequency characteristics, as well as in terms of the global azimuthal mode structure. By conducting test particle simulations in the MHD fields, we examine the dynamics of the outer zone radiation belts during this geomagnetic storm. Test particle simulations in simple analytic fields which mimic the time-dependent state of magnetospheric compression and MHD wave spectral characteristics are likewise conducted, and the results compared to the results of the full MHD/particle simulations. In this fashion, we show that the global electron response to ULF waves can be described largely in terms of the spectral characteristics of the waves and the state of magnetospheric compression, without necessarily specifying the wave fields in detail. By using these spectral characteristics to quantify appropriate diffusion coefficients, the time-dependent state of the outer zone radiation belts resulting from ULF may thus be specified through solution of the transport equations, rather than through detailed simulation.
DE: 2720 Energetic particles, trapped
DE: 2730 Magnetosphere--inner
DE: 2788 Storms and substorms
SC: SPA - Magnetospheric Physics [SM]
MN: 2003 Fall Meeting