Anisotropic cosmic ray diffusion in isotropic Kolmogorov turbulence
Anisotropic cosmic ray diffusion in isotropic Kolmogorov turbulence
复制标题
各向同性柯尔莫哥洛夫湍流中的各向异性宇宙射线扩散
DOI：
10.1093/mnras/stac1408
复制
发表时间：
2022
影响因子：
4.8
通讯作者：
Pueschel, M. J.
中科院分区：
文献类型：
--
作者：
Reichherzer, P.;Becker Tjus, J.;Zweibel, E. G.;Merten, L.;Pueschel, M. J.
了解扩散过程的时间尺度及其各向异性程度对于模拟湍流磁场中的宇宙线输运至关重要。我们发现，扩散时间尺度是各向同性的能量和湍流水平的大范围内，尽管具有有序的磁场分量的情况下，扩散张量的组件所表现出的各向异性的程度很高。讨论了经典散射关系作为平行和垂直扩散系数之间关系的描述的预测能力，并与数值模拟进行了比较。很好的协议，一个大的参数空间，转换成一个计算处方的垂直分量的经典散射关系的预测。我们讨论和比较这些发现，特别是，时间尺度变得扩散的时间尺度，粒子驻留在天文环境中，所谓的逃逸时间尺度。结果表明，特别是在高能量下，由扩散系数得到的逃逸时间可能超过扩散所需的时间尺度。在这些情况下，逃逸时间不能由扩散系数确定。
Understanding the time-scales for diffusive processes and their degree of anisotropy is essential for modelling cosmic ray transport in turbulent magnetic fields. We show that the diffusion time-scales are isotropic over a large range of energy and turbulence levels, notwithstanding the high degree of anisotropy exhibited by the components of the diffusion tensor for cases with an ordered magnetic field component. The predictive power of the classical scattering relation as a description for the relation between the parallel and perpendicular diffusion coefficients is discussed and compared to numerical simulations. Very good agreement for a large parameter space is found, transforming classical scattering relation predictions into a computational prescription for the perpendicular component. We discuss and compare these findings, in particular, the time-scales to become diffusive with the time-scales that particles reside in astronomical environments, the so-called escape time-scales. The results show that, especially at high energies, the escape times obtained from diffusion coefficients may exceed the time-scales required for diffusion. In these cases, the escape time cannot be determined by the diffusion coefficients.