Ground-Based Measurements of Magnetospheric Mass Density Using the Tsyganenko '01 Magnetic Field Model
Abstract
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.
- Publication:
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AGU Spring Meeting Abstracts
- Pub Date:
- May 2005
- Bibcode:
- 2005AGUSMSM23C..08B
- Keywords:
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- 2730 Magnetosphere: inner;
- 2740 Magnetospheric configuration and dynamics;
- 2768 Plasmasphere;
- 2788 Storms and substorms;
- 2794 Instruments and techniques