Cross Field Diffusion of Cosmic Rays: Dependence on 2-D Field Turbulence Models

Abstract

Cross field diffusion is important in efficient diffusive shock acceleration of cosmic rays for quasi‐perpendicular geometry. Cross field diffusion of cosmic rays have been discussed theoretically by quasi‐linear approximation for ‘slab’ geometry of magnetic turbulence (for example, reference [1]). In the solar wind, the presence of quasi‐two dimensional, nearly incompressional turbulence was reported by Matthaeus et. al .We discuss cross field diffusion of energetic particles numerically using compressional (C) and non‐compressional (NC) two dimensional turbulence models. For both cases of C and NC models, the diffusion is found to be composed of several regimes with different statistics. The diffusion coefficient defined in the usual way in each regime exhibits dependence to the time scale, suggesting that the underlining physical process should be described by Levy statistics. When ρ/Lb << 1, where ρ is particle Larmor radius and Lb is field turbulence correlation length, particles tend to follow equi‐...