典型甚低频电磁波对辐射带高能电子的散射损失效应

辐射带中高能电子与空间甚低频电磁波由于波粒共振相互作用发生投掷角散射, 进而沉降入稠密大气而损失. 为研究甚低频电磁波对辐射带中高能电子的散射作用机制, 本文基于准线性扩散理论, 利用库仑作用和波粒共振相互作用扩散系数的物理模型, 得到了两组典型甚低频电磁波与高能电子波粒共振相互作用的赤道投掷角弹跳周期平均扩散系数, 并分析了甚低频电磁波共振散射作用与大气库仑散射作用对不同磁壳及不同能量的辐射带电子扩散损失的影响规律. 以磁壳参数L=2.2, 能量E=0.5 MeV的辐射带电子作为算例, 采用有限差分方法数值求解扩散方程, 计算分析了电子单向通量和全向通量随时间的沉降损失演化规律. 研究结果表明: 当电子能量大于0.5 MeV, 磁壳参数大于1.6时, 甚低频电磁波的共振散射作用显著; 随着磁壳参数或电子能量的增大, 斜传播甚低频电磁波引起的高阶共振相互作用越来越大; 电子全向通量近似随时间呈指数函数形式衰减.

Diffusing loss effects of radiation belt energetic electrons caused by typical very low frequency electromagnetic wave

Radiation belt energetic electrons can interact with very low frequency (VLF) electromagnetic wave due to wave-particle resonance; then the particles are imposed to enter into the loss cone and sink to dense atmosphere resulting from changing of its pitch angle. To investigate the diffusion mechanism of interaction of VLF electromagnetic wave with radiation belt energetic electrons, according to quasi-linear diffusion theory, in this paper we use a physical model to calculate diffusion coefficients of Coulomb scatting and wave-particle resonance interaction. Bounce-averaged pitch angle diffusion coefficients of energetic electrons due to the interaction of wave-particle resonance with two groups of VLF electromagnetic waves are obtained. The influence of interaction caused by VLF electromagnetic wave and Coulomb scatting on diffusion of radiation belt energetic electrons for different L shells and various energies are analyzed. Take the case for example, where L equals 2.2 and electron energy E equals 0.5 MeV, the diffusion equation of energetic electrons are solved by using the finite difference method. The time evolutions of precipitation of directional particle flux and omnidirectional particle flux are analyzed. The results show that the resonance interaction caused by VLF electromagnetic wave plays a dominant role when E>0.5 MeV and L>1.6; the higher the L shell or electron energy value, the more significant the high order resonance interaction caused by the oblique propagation VLF electromagnetic wave will be; approximately, the omnidirectional particle flux of radiation belt energetic electrons decreases exponentially with time.