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Top and side views at phases spanning one half-period of oscillation. Phases are (a) 22.5° with visible horseshoes labelled in the chronological order of their generation, (b) 82.5°, (c) 142.5°, and (d) 202.5°. In the side view, structures closer to the camera have slightly higher magnification and thus appear to have greater spacing between them. A colour version of this figure may be found at http://gasdyn.princeton.edu.
