Example of vorticity. Examples of the vorticity scaled by a characteristic velocity v for kA/kD = 35, kMτ
= 7.5 × 10-3 and P/P0 = 0.024. For clarity error bars are only given for a single run. The thick horizontal line segments denote the mean value up to the time when the vortex contracts to a semi-aster, and are plotted up to this time.