DYNAMIC CURRENT SHEETS WITH LOCALIZED ANOMALOUS RESISTIVITY

Two-dimensional compressible magnetohydrodynamic simulations of curren t sheet dynamics under the influence of localized anomalous resistivit y are presented. The system is initially perturbed by several spots of anomalous resistivity distributed in the sheet. Following a phase of induced tearing resulting from the initial perturbation, magnetic isla nd coalescence occurs until one island persists. Finally the evolution becomes eruptive, dominated by the acceleration and ejection of a pla smoid, as a consequence of the amplification of a small initial asymme try after a few 10(2) Alfven times. These processes are accompanied by strong enhancements of the current density. It exceeds the threshold of kinetic instability repeatedly and leads to recurrence of anomalous resistivity, which drives the evolution. Jets are formed, driven by h eld line reconnection and locally enhanced dissipation at dominant X-p oints. The conversion of magnetic energy into kinetic energy is most e fficient during the acceleration phase of the plasmoid. The evolution becomes more impulsive and leads to stronger current density enhanceme nts for higher Lundquist numbers. (C) 1996 American Institute of Physi cs.