磁层高能粒子运动的Fokker Planck方程位置项扩散系数研究

利用准线性理论计算了磁层高能粒子运动的Fokker Planck方程在可观测相空间的位置项扩散系数，并与绝热不变量径向扩散系数进行对比分析.研究发现:位置项扩散系数随径向距离呈现R6的比例关系快速增大.相同径向距离条件下，由于空间位置项z分量的作用，高纬度地区的位置项扩散系数小于低纬度地区.通过与径向扩散系数对比发现，两者具有相同的量级，但两者的相对大小需要根据具体的扰动形态进行分析.此研究对使用测试粒子模拟磁层高能粒子运动，尤其是根据引导中心理论，利用蒙特卡洛方法求解磁层高能粒子运动的Fokker Planck方程，建立磁层空间高能粒子运动的精细化模型具有重要意义. 

Study on the Position Diffusion Coefficients of Fokker Planck Equation of Magnetosphere Energetic Particle

In this paper, the quasi-linear theory is used to calculate the diffusion coefficients of the Fokker Planck equation of energetic particles in the observable phase space, and the comparison with the adiabatic invariant radial diffusion coefficients is carried out. The main findings are as follows. The diffusion coefficients of the position items will increase rapidly with the radial distance. Under the same radial distance, the diffusion coefficient of the position items in the high latitude will be smaller than that in the low latitude. Compared with the radial diffusion coefficient, it is found that the two have the same magnitude, but the relative size of the two needs to be analyzed according to the specific disturbance form. This study will use the test particles to simulate the motion of energetic particles in the magnetosphere, especially the guidance center theory, and use the Monte Carlo method of stochastic partial differential to solve the Fokker Planck equation of the motion of energetic particles in the magnetosphere.