Upper panel: case of a parallel shock in jets: ionisation fraction, x, versus density of neutrals, n, for U_sh = 40 and 160 km s^-1, B = 50 μG and 1 mG, and T = 10⁴ K. Lower panel: case of parallel (left) and perpendicular (right) shocks on protostellar surfaces: ionisation fraction, x, versus magnetic field strength, B, for U_sh = 260 km s^-1, T = 9.4 × 10⁵ K, and n = 1.9 × 10¹² cm^-3. Colour maps show values of E_max for protons and cyan contours delimit the regions where E_max reaches its maximum constant value shown in GeV in each subplot. Vertically hatched regions refer to combinations of parameters corresponding to strong wave damping (R< 1).