Critical velocities of interstellar shocks for $n_{\mathrm{H}}^0$ = 0.1 cm⁻³ (top panel) and 1 cm⁻³ (bottom panel). The solid and dash-dotted lines show the magnetosonic speed computed in the ionized fluid (Eq. (19)) and the neutral fluid (Eq. (18)), respectively. The colored areas highlight the range of velocities over which stationary shocks are C-type (red), CJ-type (blue), and J-type (green) shocks. The transition between C-type and CJ-type shocks (dashed line) is estimated as the point where the maximum postshock thermal pressure is equal to the maximum magnetic pressure allowed by an adiabatic compression. The gray points indicate the values of the shock velocity and transverse magnetic field strength explored in the grid of models. The red dot highlights the position of the standard model.