Abstract

The acceleration of energetic particles and their propagation in magnetic fields of the solar wind and the Galaxy is a topical astrophysical problem. Cosmic rays (CR) affect communications and the operation of on-board spacecraft electronics and disturb the magnetosphere and the ionosphere of the Earth. The scattering of particles by magnetic-field irregularities is the primary mechanism governing the CR propagation in the interplanetary medium. If the scattering of energetic particles in the interplanetary medium is relatively inefficient (i.e., the mean free path is comparable to the heliocentric distance), a kinetic equation should be used to characterize the CR propagation. The Fokker–Planck kinetic equation is used to analyze the propagation of charged energetic particles in a magnetic field represented as a superposition of a mean uniform field and magnetic inhomogeneities of various scales. This kinetic equation corresponds to multiple small-angle scattering, and its collision integral characterizes particle diffusion in the momentum space. A system of differential equations for the spherical harmonics of the CR distribution function is obtained based on the kinetic equation. The CR transport equations are derived and solved. The evolution of the CR distribution function under anisotropic scattering of particles by magnetic-field fluctuations is examined. It is demonstrated that the angular distribution function of particles depends to a considerable extent on the degree of their scattering anisotropy. The temporal dependence of the CR distribution function is analyzed, and the parameter characterizing the scattering anisotropy is estimated.

中文翻译：

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磁场起伏对粒子各向异性散射的宇宙射线分布函数

摘要

高能粒子的加速及其在太阳风和银河系磁场中的传播是一个局部的天体物理学问题。宇宙射线（CR）影响着航天器电子设备的通信和运行，并扰乱了地球的磁层和电离层。磁场不规则引起的粒子散射是控制CR在行星际介质中传播的主要机制。如果高能粒子在行星际介质中的散射效率相对较低（即，平均自由程可与日心距相媲美），则应使用动力学方程来表征CR的传播。福克-普朗克动力学方程用于分析带电高能粒子在磁场中的传播，该磁场表示为平均均匀场和各种尺度的磁不均匀性的叠加。该动力学方程对应于多个小角散射，其碰撞积分表征了动量空间中的粒子扩散。基于动力学方程，获得了一个CR分布函数的球谐函数的微分方程组。CR传输方程式被推导和求解。研究了磁场波动引起的颗粒各向异性散射下CR分布函数的演变。结果表明，颗粒的角分布函数在很大程度上取决于其散射各向异性的程度。