Comparison of the trajectories in the v_x − v_y space of two typical energetic tracked drifting (a) and ambient (b) protons, for the double shock case in red and for the single shock case in blue. (We note that their initial velocities might be different from the species bulk speed (v_x = 350 km s⁻¹), since the protons are initiated with an initial temperature.) (c) Final energy spectra of the ions for the two configurations and (d) zoom on the range from 10 to 30 keV.