Weak Turbulence and Quasilinear Diffusion for Relativistic Wave-Particle Interactions Via a Markov Approach
Weak Turbulence and Quasilinear Diffusion for Relativistic Wave-Particle Interactions Via a Markov Approach
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DOI：
10.3389/fspas.2021.805699
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发表时间：
2022-01-14
影响因子：
3
通讯作者：
Neukirch, Thomas
中科院分区：
文献类型：
--
作者：
Allanson, Oliver;Elsden, Thomas;Neukirch, Thomas
我们在俯仰角和能量空间中推导了相对论带电粒子动力学的弱湍流和拟线性模型，这是由于电磁波与均匀背景磁场平行传播（反）的相互作用。我们使用一种马尔可夫方法，从考虑单粒子在规定电磁场中的运动开始。这种马尔可夫方法有许多好处，包括：1)在更一般的弱湍流理论和标准共振扩散拟线性理论（如通常用于辐射带和太阳风建模）之间明显的自洽关系；2)福克-普朗克方程的一般性质，不需要对其形式作任何预先假设就可以推导出来；3) Fokker-Planck方程的形式和输运系数在给定特定时间尺度上的明显依赖性。我们推导出的拟线性扩散系数本身并不新鲜，但这种使用马尔可夫框架对弱湍流和拟线性理论的简明推导和讨论在物理上是非常有指导意义的。本文提出的结果为未来的研究奠定了基础，这些研究考虑了本手稿中所作的一些假设可以放松的现象。
We derive weak turbulence and quasilinear models for relativistic charged particle dynamics in pitch-angle and energy space, due to interactions with electromagnetic waves propagating (anti-)parallel to a uniform background magnetic field. We use a Markovian approach that starts from the consideration of single particle motion in a prescribed electromagnetic field. This Markovian approach has a number of benefits, including: 1) the evident self-consistent relationship between a more general weak turbulence theory and the standard resonant diffusion quasilinear theory (as is commonly used in e.g. radiation belt and solar wind modeling); 2) the general nature of the Fokker-Planck equation that can be derived without any prior assumptions regarding its form; 3) the clear dependence of the form of the Fokker-Planck equation and the transport coefficients on given specific timescales. The quasilinear diffusion coefficients that we derive are not new in and of themselves, but this concise derivation and discussion of the weak turbulence and quasilinear theories using the Markovian framework is physically very instructive. The results presented herein form fundamental groundwork for future studies that consider phenomena for which some of the assumptions made in this manuscript may be relaxed.