Numerical investigation of the cosmic-ray scattering anisotropy and Bohm diffusion in space plasmas




We employ a recently developed test-particle simulation code to explore the Bohm diffusion and the scattering anisotropy of charged particles interacting with magnetic turbulence. By computing parallel and perpendicular mean free paths, it is shown that a dominant mean magnetic field and a large particle mean free path along the mean magnetic field break the scattering symmetry. In such cases, a strong scattering anisotropy is found, which is in good agreement with recent analytical calculations. It is also shown that the assumption of the Bohm diffusion in isotropic turbulence is only valid for some special cases.