Simulation of accelerated particle diffusion in collisionless shocks with an admixture of heavier-than-hydrogen ions

We report on the results of hybrid simulation of diffusive shock acceleration of ions with different charge-to-mass ratios in quasi-parallel collisionless shocks. We consider a hydrogen medium with dynamically insignificant admixtures of helium and carbon ions in various charge states. Spatial regions of applicability of the Bohm approximation as well as the quasi-linear diffusion theory are determined. The possibility of nondiffusive propagation in regions far ahead of the shock is considered.