Temporal development of the ion density together with the configuration of magnetic field lines. Spatial profiles of ion density normalized to the initial density N
0 at different times are shown by the hot-scale colormap. The magnetic field lines and the location of the inner boundary are indicated by the cyan lines and the magenta circle. The results from the low-resolution run (Umeda and Ito 2014) and the high-resolution run are shown in the top and bottom panels, respectively.