Upper panel: integral of the isotropic scattering coefficient, D, as obtained from a numerical simulation (black solid line) for particles with a normalized rigidity R = γv/(Ωℓ₀) = 0.1. A linear fit (red dashed line) yields the value for D = 1.2324 × 10^-3   Ω itself; for clarity, the fit line has been shifted downward. Lower panel: pitch-angle mean square displacement as obtained from the simulation (black solid line) in comparison with the analytical form (red dashed line) from Eq. (18), which uses the value for D that was obtained above. (This figure is available in color in electronic form.)