Average pitch angles as a function of energy shown for PIC particles over the whole simulation domain, as well as PIC particles taken only from the region of active acceleration highlighted in the inset with a red box. The inset also shows magnetic-field lines and particles colored by energy, ranging from blue (γ ≈ 5) to red (γ ≈ 100). γ^−0.66 and γ^−0.9 power laws are included for reference. Measurements are made via fully relativistic Lorentz transformations to the E × B frame of the plasma. Particles in the process of acceleration have pitch angles declining very close to γ⁻¹.