Trajectories followed by interstellar shocks in a proton density versus thermal pressure diagram (see Fig. 5). Each panel corresponds to different values of the initial density $n_{\mathrm{H}}^0$ (top labels) and transverse magnetic field B₀ (right labels). The different curves correspond to the following values of the shock velocity ordered from top to bottom trajectories: 500, 450, 400, 350, 300, 250, 200, 150, 120, 100, 90, 80, 70, 60, 50, 40, 30, 20, and 10 km s⁻¹. Colored trajectories correspond to J-type shocks, gray trajectories to CJ-type shocks, and black trajectories to C-type shocks. The black curve common to all panels indicates the thermal equilibrium state of the diffuse gas as a function of the proton density obtained for G₀ = 1 (see Fig. 1). Light gray lines are isothermal contours from 1 to 10⁷ K (from bottom right to top left). We note that the trajectories of low-velocity shocks are not always visible as they only slightly perturb the gas from its original state.