COALESCENCE OF MAGNETIC ISLANDS INCLUDING ANOMALOUS RESISTIVITY

Two-dimensional compressible magnetohydrodynamic simulations of the co alescence instability in a low-beta plasma are presented in which anom alous resistivity is permitted to occur. The instability is considered in a uniform current sheet configuration, initially perturbed by an i nfinite chain of spots of anomalous resistivity. The two phases of the instability known from simulations based on the Fadeev equilibrium - ideal and resistive - can clearly be distinguished also in this config uration. It is found that the conversion of magnetic energy into kinet ic energy dominates Ohmic heating. The main energy release occurs with in a few Alfven transit times. The scaling of several key parameters i n the current layer formed between the coalescing islands is compared to the scalings obtained with uniform resistivity. The numerical resul ts indicate that the peak reconnection rate decreases toward large Lun dquist numbers (S much greater than 10(4)) as S-a with a = 1/5 - 1/3 a nd that a transition to slow reconnection (a similar to 1/2) may occur at S greater than or similar to 10(7), where S is based on the backgr ound resistivity. (C) 1997 American Institute of Physics.