Cosmic-Ray Momentum Diffusion In Magnetosonic Versus Alfvenic Turbulent Field

. Energetic particle transport in a finite amplitude magnetosonic and Alfv´enic turbulence is considered using Monte Carlo particle simulations, which involve an integration of particle equations of motion. We show that in a low- β plasma cosmic ray acceleration can be the most important damping process for magnetosonic waves. Assuming such conditions we derive the momentum diffusion coefficient D p for relativistic particles in the presence of anisotropic finite-amplitude turbulent wave fields, for flat and Kolmogorov-type turbulence spectra. We confirm the possibility of larger values of D p occurring due to transit-time damping reso- nance interaction in the presence of isotropic fast-mode waves in comparison to the Alfv´en waves of the same amplitude (cf. Schlickeiser & Miller 1998). The impor- tance of quasi-perpendicular fast-mode waves is stressed for the acceleration of high velocity particles.