2D profiles of vertical (top) and horizontal (bottom) velocity in the red giant model at x = 7.77 × 10¹¹ cm (marked by white vertical lines in Fig. 4). Locations where the vertical velocity  Mach (supersonic down-flows, top panel) are marked with white contours, those where v_z and v_h exceed 1 Mach are contoured in black (contours start at Mach =  ± 1.0 and are drawn at every  ± 0.5 Mach thereof).