Snapshots of the radial velocity in the inwardly propagating pulse of rarefaction, as a function of the radial coordinate r. Different colours and thickness correspond to two different initial amplitudes of the pulse. Red (thick) line corresponds to the instants of time t = 0.3 s (solid), t = 0.5 s (dotted), t = 0.7 s (dashed), and blue (thin) to t = 0.5 s (solid), t = 0.8 s (dotted), and t = 1.1 s (dashed). The radial coordinate is measured in units of r₁.