Abstract:
The 16 years’ accumulation of magnetospheric plasma analyzer data from seven Los Alamos geosynchronous satellites is used for a statistical study on the hot electron temperature (0.03~45 keV) and the spacecraft (S/C) surface sunlit charging potential in the plasma sheet region at the geosynchronous orbit and their dependence on the local time (LT) and the epoch time (ET) with respect to storms of three categories: moderate, intense and super storms, based on different geomagnetic activity levels as measured by Dst index corrected by the solar wind dynamic pressure. As a function of LT and three categories of storms, the measured S/C surface charging potential is shown with distinct spatial and temporal distributions well consistent with hot electron temperature behaviors. The area of the most probable charging and of a high negative level expands following a systematic trend with increasing storm size, and the post-midnight region for moderate storms will expand to the LT=21~04 region for super storms. The most probable charging with a high negative level dominates at about 3 hours before and 2 hours after the moderate storm peak, just at the intense storm peak and in the recovery phase of the super storms. However, there is no systematic relations between a large negative charging (>8 kV) and the magnitude of storms as evidenced in this study; it can occur in all geomagnetic activity levels and perhaps more likely in the pre-noon sector during the moderate storm peak time.
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