HR: 1330h
AN: SM23C-08    [Abstracts]
TI: Ground-Based Measurements of Magnetospheric Mass Density Using the Tsyganenko '01 Magnetic Field Model
AU: * Berube, D
EM: dberube@igpp.ucla.edu
AF: Department of Earth and Space Sciences, University of California, Los Angeles, 595 Charles Young Drive East 3806 Geology Bldg., Los Angeles, CA 90095-1567 United States
AU: Moldwin, M B
EM: mmoldwin@igpp.ucla.edu
AF: Department of Earth and Space Sciences, University of California, Los Angeles, 595 Charles Young Drive East 3806 Geology Bldg., Los Angeles, CA 90095-1567 United States
AU: Moldwin, M B
EM: mmoldwin@igpp.ucla.edu
AF: Institute of Geophysics and Planetary Physics, UCLA, 595 Charles Young Drive East, Los Angeles, CA 90095-1567 United States
AU: Ahn, M
EM: markahn@ucla.edu
AF: Department of Earth and Space Sciences, University of California, Los Angeles, 595 Charles Young Drive East 3806 Geology Bldg., Los Angeles, CA 90095-1567 United States
AB: The plasma mass density of the inner magnetosphere can be inferred from resonant frequencies of closed magnetospheric field lines. The field line resonant (FLR) frequency depends on field line length, magnetic field strength, and the mass density along the field line. In many studies, field line length and magnetic field strength are approximated by a dipole. However, during periods of increased geomagnetic activity, the inner-magnetospheric field configuration can differ significantly from a dipole. In order to accurately determine mass density, a better approximation of the magnetic field must be used. In this study, FLR frequencies measured by pairs of stations in the MEASURE array (L=1.7-3.2) are used to infer equatorial plasma mass density. Field strength and field line length are computed from the Tsyganenko '01 empirical magnetic field model. The resulting mass densities are compared to those obtained assuming a pure dipole. Data from all local times, seasons, and activity levels are used. The results show the greatest differences during the most disturbed times, demonstrating that in the plasmasphere (for L < 3.2) the dipole magnetic field approximation is valid except during extreme levels of geomagnetic activity.
UR: http://measure.igpp.ucla.edu/berubeAGUS05/
DE: 2730 Magnetosphere--inner
DE: 2740 Magnetospheric configuration and dynamics
DE: 2768 Plasmasphere
DE: 2788 Storms and substorms
DE: 2794 Instruments and techniques
SC: SPA-Magnetospheric Physics [SM]
MN: 2005 Joint Assembly