光谱分辨cosmic ray流体力学-- I.光谱方案
Spectrally resolved cosmic ray hydrodynamics -- I. Spectral scheme
摘要：
宇宙线质子是许多天体物理系统的重要组成部分。过程，如CR注射，冷却，绝热变化，以及通过介质的主动CR运输强烈修改CR动量分布，必须考虑到在流体动力学模拟。我们提出了一种有效的新的数值方案，通过求解具有少量光谱箱（10 - 20）的Fokker-Planck方程来精确计算粒子分布函数的演化，这需要包括每个计算流体元素的全光谱。分布函数由分段幂律表示，并且不强制连续，这使得能够实现频谱的最佳表示。Fokker-Planck方程采用双矩方法求解，得到CR数和能量密度。该方案的低数值扩散减少了数量级的数值误差相比，经典的计划与分段常数谱表示。用这种方法不仅可以在磁流体动力学模拟中精确地计算CR的谱演化，而且可以计算它们的动力学影响以及CR电离。这使得更精确的天体物理等离子体模型，如星际介质，并直接与观察比较。
英文摘要：
Cosmic ray (CR) protons are an important component in many astrophysical systems. Processes like CR injection, cooling, adiabatic changes as well as active CR transport through the medium strongly modify the CR momentum distribution and have to be taken into account in hydrodynamical simulations. We present an efficient novel numerical scheme to accurately compute the evolution of the particle distribution function by solving the Fokker-Planck equation with a low number of spectral bins (10 - 20), which is required to include a full spectrum for every computational fluid element. The distribution function is represented by piecewise power laws and is not forced to be continuous, which enables an optimal representation of the spectrum. The Fokker-Planck equation is solved with a two-moment approach evolving the CR number and energy density. The low numerical diffusion of the scheme reduces the numerical errors by orders of magnitude in comparison to classical schemes with piecewise constant spectral representations. With this method not only the spectral evolution of CRs can be computed accurately in magnetohydrodynamic simulations but also their dynamical impact as well as CR ionisation. This allows for more accurate models for astrophysical plasmas, like the interstellar medium, and direct comparisons with observations.
机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。
