Credit: Yi-Min Huang, Princeton University
In each panel, the upper half shows the current density, and the lower half shows the plasma outflow velocity along the horizontal direction at special times during the simulation. Panel (a) shows the disruption of the primary reconnecting current sheet when the typical size of the plasmoids (magenta lines) exceeds the inner layer width (dashed lines). After the disruption, secondary current sheets between plasmoids become extended and thin, panel (b). In the next level of disruption, extended secondary current sheets become unstable to the plasmoid instability, panel (c). This self-similar, fractal-like process of current sheet disruption leads to a hierarchy of plasmoids of different sizes, panel (d).