Ratio of the electron temperature upstream and downstream (T_e,2/T_i,2), resulting from different assumptions. The dashed line corresponds to Eq. (19) (adiabatic heating and thermalisation), the solid line corresponds to Eq. (10). For illustrative purposes we also show the effect of adiabatic compression alone (dotted line) and the upstream and upstream temperature ratios for ions (dot-dashed line).