Data assimilative modeling of the Earth's radiation belt electrons based on the Arase satellite observations

The Arase satellite, a scientific satellite dedicated to the detection of the Earth's radiation belts, was successfully launched on 20 December 2016. After the termination of the Van Allen satellites in October 2019,the Arase satellites continue to operate normally and provide high-quality observations. In this paper, the data assimilation modeling of the spatial and temporal evolution process of the electron flux in the outer radiation belts of the Earth (L* = 3 similar to 7) for the period of April 2017 to March 2022 is achieved by using the Kalman filter method in conjunction with the electron flux observation data from the high-energy electron detector of the Arase satellite and the numerical model of the three-dimensional radiation belts based on the Fokker-Planck diffusion equation. The results show that the assimilation model effectively compensates for the missing observation of Arase satellite data for electrons with high equatorial pitch angles, and reconstructs the long-term dynamic evolution process of radiation belt electrons with different energies and pitch angles at different L* andtheir response characteristics to geomagnetic activities. By calculating the Pearson correlation coefficient, meanerror, mean absolute error and mean square error between the data assimilation results of the electron fluxes andthe satellite observations, it was found that the electron flux assimilation results and the observations were inoverall agreement. By calculating the innovation vectors in the assimilation process, we analyze the degree ofcorrection of the satellite observations to the simulation results of the numerical model of the radiation belts andits dependence on the electron energy and L*, which provides significant references for the analysis of themissing physical mechanisms of the numerical model of the radiation belts as well as the subsequentimprovement and refinement of the model.