Monte-Carlo simulations of the interaction between Alfven waves and energetic particles

Pitch-angle scattering in solar particle events is often described as a diffusive processes. However, the concept of the diffusion approximation breaks down if the frequency of the scattering events is small compared to the observation time. In this work we investigate the effect of rare discrete scattering events compared to frequent (diffusive) scattering, using two different models which describe energetic particle propagation in the heliosphere. For a guiding center approximation we directly compare different scattering frequencies and mean free path lengths while keeping the diffusion coefficient constant. In an ab-initio model we calculate the exact particle motion in a Parker field superimposed with Alfvenic fluctuations. For a given spectrum of fluctuations one can create different Alfven wave configurations which correspond to different mean free path values. For both models pitch-angle anisotropy and intensity profile both depend significantly on scattering frequency resp. mean free path.