Numerical study of Cosmic Ray Diffusion in MHD turbulence

TL;DR

This paper investigates cosmic ray diffusion in magnetohydrodynamic turbulence through numerical simulations, comparing results with analytical models and identifying key scattering mechanisms and transport behaviors.

Contribution

It provides a detailed numerical analysis of cosmic ray diffusion in MHD turbulence, highlighting the dominant scattering processes and validating analytical predictions.

Findings

Qualitative agreement with analytical models

Non-resonant mirror interactions dominate scattering

Magnetic field wandering influences perpendicular transport

Abstract

We study diffusion of Cosmic Rays (CRs) in turbulent magnetic fields using test particle simulations. Electromagnetic fields are produced in direct numerical MHD simulations of turbulence and used as an input for particle tracing, particle feedback on turbulence being ignored. Statistical transport coefficients from the test particle runs are compared with earlier analytical predictions. We find qualitative correspondence between them in various aspects of CR diffusion. In the incompressible case, that we consider in this paper, the dominant scattering mechanism occurs to be the non-resonant mirror interactions with the slow-mode perturbations. Perpendicular transport roughly agrees with being produced by magnetic field wandering.