The second approach is illustrated in Fig. 5 for various pitch
angles. By evaluating Eq. (3), a Fokker-Planck coefficient is obtained
that depends both on the time and on the pitch-angle cosine.
Plotted as a function of time, the transition to the diffusive
regime can be seen for times t 5Ω−1. For times t 50Ω−1,
it is admissible to take asymptotic values for the Fokker-Planck
coefficient as a function of the pitch-angle cosine, i.e., Dμμ(μ).