Shock nature diagnostic in the termination region of a YSO jet for different jet and ambient densities, for v_j = 300 (left) and 1000 km s⁻¹ (right). The pink region indicates when the forward shock (FS) and the reverse shock (RS) are radiative, while the larger green region indicates when the forward shock is radiative and the reverse shock is adiabatic. Grey colour indicates an adiabatic forward shock and a radiative reverse shock while the yellow area shows when both shocks are adiabatic. The white dot indicates the parameters used in the numerical simulations in Sect. 4.