Plot showing pitch-angle cosine distributions, f(cos θ _PA), corresponding to γ _PA = −4 (top), γ _PA = 0 (middle), and γ _PA = 4 (bottom). A value of cos θ _PA of 1 (− 1) corresponds to the non-thermal particle's momentum being directed parallel (anti-parallel) to the loop axis. A pitch-angle cosine of zero corresponds to the non-thermal particle's momentum being directed perpendicular to the loop axis.