Electron Environment Characteristics and Internal Charging Evaluation for MEO Satellite

By analyzing the newly released in situ data in medium earth orbit (MEO) of global positioning system satellites, we studied the spatiotemporal distribution and statistical characteristics of electrons over one solar cycle. The Weibull distribution of daily-averaged flux cumulative occurrence probability is proven. For >2-MeV electron flux, the determination coefficient of Weibull fitting is 99.92%. In the magnetic storm of late July 2004, the radial diffusion of electrons to low L-shell position was obvious. The center of 0.04-MeV electrons moved inward from L = 6 to L = 4.3 in the main phase and moved outward slowly in the recovery phase. In 0-4 MeV range, the in situ electron flux data are consistent with the AE9 mean and MEO-v2 model. The percentile of the AE9 model is also validated. The differential spectra are fitted based on exponential function at different percentiles. We also develop a rapid analysis method of internal charging in a changing electron environment. Using this method, we find that the electric field of internal charging fluctuates a lot because of the time-varying electron environment in MEO. The charging processes of different dielectrics (time constant ranges from 1 day to 100 days) in one solar cycle are also simulated. The longer the time constant, the bigger is the maximum charging electric field. But the worst case flux needed for discharging hazard evaluation is smaller. The daily-averaged worst case flux for charging assessment is not applicable.