In Fig. 4, the time evolution of a Kolmogorov-Smirnov (KS)
test statistic is shown, which is obtained from the comparison of
the pitch-angle distribution, f (μ, t), with the initial pitch-angle
distribution, f (μ0, 0). Because the latter is obtained from a uniform
random deviate, the usual result of an isotropized distribution
due to pitch-angle diffusion leads to the requirement that the
pitch-angle distribution be uniform. A linear fit of the otherwise
relatively volatile KS statistic shows that, on average, the P value
(i.e., the probability that the given distribution agrees with the assumed
one) of the KS test is well above 80%; this confirms that
the pitch-angle distribution remains compatible with the initial
distribution.