基于Fortran语言的地球外辐射带电子三维数据同化建模

Three-dimensional data assimilative model of the Earth's outer radiation belt electrons based on the Fortran language

开发地球电子辐射带的数据同化模型,对于理解辐射带电子的动态演化过程和辐射带空间天气预报具有重要意义.结合范阿伦卫星的辐射带电子观测数据和外辐射带三维扩散模型,采用卡尔曼滤波算法,本文开发了基于Fortran语言的外辐射带电子三维数据同化模型(Three-dimensional Data Assimilative Model of Outer Radiation belt Electrons,简称TDAMORE),实现对L^(*)=3~7、能量范围为0.1~5 MeV、投掷角范围为5°~90°的外辐射带电子时空变化过程的三维重构.通过对2018年8月期间外辐射带电子通量演化过程的重构,证实TDAMORE模型可以较好地重现不同能量和不同投掷角电子通量在磁暴前后的演化特征.通过分析电子通量的观测和同化结果之间的相关系数、平均误差、平均绝对误差和均方误差,发现对于能量低于4 MeV的电子,观测与同化结果之间的相关系数基本大于0.8且误差相对较低.而对于更高能量的电子,观测与同化结果之间的误差相对较高,这可能是同化模型忽略了电磁离子回旋波对电子的散射损失导致的.

Development of a data assimilative model for the Earth's electron radiation belts is important for understanding the dynamic evolution of radiation belt electrons and forecasting radiation belt space weather. Based on Van Allen Probes observations and the three-dimensional diffusion model of the outer radiation belt, we utilize the Kalman filtering algorithm to develop a Three-dimensional Data Assimilative Model of Outer Radiation belt Electrons (TDAMORE) based on the Fortran language, which is applied to radiation belt electrons at energies of 0.1~5 MeV and pitch angles of 5°~90° at L^(*)=3~7. By reconstructing the evolution process of electron fluxes in the outer radiation belt during August 2018, we confirm that the TDAMORE model can well reproduce the evolution characteristics of electron fluxes with different energies and pitch angles before and after magnetic storms. By analyzing the correlation coefficient, mean error, mean absolute error and mean squared error between the observed and assimilative electron fluxes, we find that for electrons with energy less than 4 MeV, the correlation coefficient is basically greater than 0.8 and the error is relatively low. For higher energy electrons, the error between the observed and assimilative results is relatively high, which may be due to the absence of the scattering loss of electrons by electromagnetic ion cyclotron waves.