Trajectory of a shocked fluid particle from the ambient medium to the post-shock region obtained in the standard model. The trajectory is displayed in a proton density–thermal pressure diagram to highlight the phase transition from the WNM to the CNM induced by a shock at 80 km s⁻¹. A fluid particle initially evolves through the radiative precursor (pink). As it crosses a shock front, it undergoes three successive regimes: an adiabatic heating (red curve) followed by a quasi-isobaric cooling (green curve), and, finally, a quasi-isochoric cooling (blue curve) as the magnetic pressure becomes dominant in the post-shock gas. The black curve indicates the thermal equilibrium state of the diffuse gas obtained for G₀ = 1 (see Fig. 1 of Paper I). Light grey lines are isothermal contours from 1 to 10⁶ K (from bottom right to top left). Note that these isocontours are not evenly spaced due to the change in the number of particles in a gas at high temperature (see Fig. 5 of Paper I).