Pressure distribution (logarithmic scale) for the simulation including a propagating density perturbation. The three panels show the pressure in the stationary (equilibrium) state, after a time t = 0.9z₀/c and, on the left, at t = 5z₀/c. The figure clearly shows the high-pressure wake induced by the perturbation in the jet. In the last panel, the inward shift of the recollimation nozzle is clearly visible.