Snapshot of Run H with vortex arcs. All plots display the warped τ = 1 surface in gray color. Panel a) shows the swirling strength (green volume rendering), red arrows indicate the features discussed in the text. Panels b) and c) show selected streamlines and the vertical velocity (red/blue volume rendering). The streamlines are colored according to the horizontal velocity in the approximate direction of the big arc. The size of the box shown is 1.3  ×  1.4  ×  0.7   Mm³. The blow-up in panel a) contains the feature presented in Fig. 12.