The problem of cosmic ray scattering in magnetohydrodynamic turbulence is revisited using a recently developed Monte Carlo simulation code. Diffusion coefficients are obtained using magnetostatic turbulence, slab Alfvénic turbulence with and without electric fields and isotropic magnetosonic turbulence with and without electric fields. All non-magnetostatic simulations are carried out for different values of the Alfvén velocity so that the effects of different particle to Alfvén velocity ratios can be studied. For slab turbulence, it is shown that Alfvén waves guarantee the recovery of diffusion, as predicted by analytical studies. The inclusion of electric fields, however, immediately leads to superdiffusion, if the Alfvén velocity is not too small. Furthermore, the energy gain through stochastic acceleration processes is investigated both qualitatively and quantitatively. The comparison with previous simulation reveals both similarities and interesting differences.
Simulation of Alfven-wave-resonant-particle interaction