Periodic release of alternating sign magnetic structures. Volume renderings of B² are shown from case M2 at times ﹩t=200.0﹩, 205.5, 211.0, 216.5, 222.0, 227.4. Tubelike strong magnetic structures emerge from the velocity shear driving region first on one side (the left, or ﹩y> y_{m}/ 2﹩, panels [a], [b], and [c]) and then the other (right, or ﹩y< y_{m}/ 2﹩). With these parameters, the structures diffuse when out of the localized shear driving region.