Dynamics of the Plasmoid-unstable Regime in Different Multiple-current Plasmas
The dynamics of plasmoid instability in multiple-current plasmas with different system sizes is investigated by means of resistive magnetohydrodynamic simulations. As the system size is increased, the secondary current sheets become very long, producing more plasmoids. It is found that the dependence on resistivity η of the number of plasmoids changes from no clear scaling for small system size, to scaling in ∼η{sup −1} for large system size. Moreover, increasing the current length of the system weakens the negative dependence of the early growth rate of the monster plasmoid on η. This is qualitatively different from the reconnection rate for a single-current sheet, where it usually has a positive dependence on η or is independent of η. In addition, increasing the current length significantly increases the maximum width of the monster plasmoid in the low-η regime, manifesting a scaling ∼η{sup −0.4}.