HR: 0800h
AN: SM21A-0302    [Abstracts]
TI: Plasmaspheric Ion Refilling Rates
AU: Obana, Y
EM: yuki.obana@newcastle.edu.au
AF: University of Newcastle, School of Mathematical and Physical Sciences, Callaghan, NSW 2308, Australia
AU: * Menk, F W
EM: fred.menk@newcastle.edu.au
AF: University of Newcastle, School of Mathematical and Physical Sciences, Callaghan, NSW 2308, Australia
AB: Recently there has been intense interest in estimation of the equatorial mass density based on measurements of field line resonance frequencies with ground magnetometers. Using cross-phase analysis of magnetometer array data, we determined the equatorial mass density during a moderate geomagnetic storm that followed several days of magnetically quiet conditions. Early in the storm recovery phase (Kp = 6+), the field line eigenfrequency over L = 2.3 – 3.8 was unusually high, corresponding to very low mass densities and flux tube depletion. Over the next few days the eigenfrequency at these L values progressively decreased, indicating refilling of the flux tube to pre-storm levels, superimposed upon diurnal variations. By comparing density measurements we determined the daytime ion refilling rates and fluxes at the 1000 km level for the L = 2.3, 2.6, 3.3, and 3.8 flux tubes. The upward ion fluxes decreased with increasing L-value, being around 4 x 10⁸ amu/cc/sec at L=2.3 and 1.5 x 10⁸ amu/cc/sec at L=3.8, respectively. We compare these observations with daytime upward electron fluxes measured by VLF whistler techniques, and investigate the L-value dependence in refilling rate. The latter may be attributed to solar zenith angle control of ion production rates.
DE: 2730 Magnetosphere: inner
DE: 2736 Magnetosphere/ionosphere interactions (2431)
DE: 2752 MHD waves and instabilities (2149, 6050, 7836)
DE: 2768 Plasmasphere
SC: SPA-Magnetospheric Physics [SM]
MN: 2007 Fall Meeting