A numerical study of the pitch-angle scattering of cosmic rays

We present the results of a careful study of finite-difference solutions to the problem of cosmic-ray transport, including pitch-angle scattering. In contrast to some recent studies, we confirm the diffusion approximation in cases where the scattering mean free path is small compared with other length scales. The reasons for the discrepancy with the conclusions of Gombosi and Owens are discussed.