Rate of change of parallel (blue), perpendicular (red), and total (green) thermal energy of 160,000 tracked particles from the ﹩{\beta }_{{\rm{i}}0}=1﹩ run, segregated into superthermal (﹩{w}_{\perp }\gt {v}_{\mathrm{thi}0};﹩ top) and subthermal (﹩{w}_{\perp }\lt {v}_{\mathrm{thi}0};﹩ bottom) populations resulting from all events above “threshold,” the minimum factor by which ﹩{w}_{\perp }^{2}/{w}_{\parallel }^{2}﹩ changes (up or down) within a time interval 5 · 2π/Ω_i0 (see footnote 7). The shaded regions indicate the variation of these rates as a function of time interval (from 4 · 2π/Ω_i0 to 8 · 2π/Ω_i0). For w_⊥ > v_thi0 in particular, ﹩{w}_{\parallel }^{2}﹩ and ﹩{w}_{\perp }^{2}﹩ change much more than ﹩{w}_{\mathrm{tot}}^{2}﹩ does, consistent with pitch-angle scattering. (Here, “∥” and “⊥” are measured with respect to the magnetic field at the location of each particle.)