COLLISIONLESS M=1 RECONNECTION IN TOKAMAKS

In high temperature tokamak regimes, the m = 1 reconnecting mode is go verned by two fluid effects associated with the electron skin-depth d( e) = c/omega(pe) and the ion sound radius rho(s) = c(s)/Omega(ci). To clarify the early nonlinear dynamics of this mode, numerical simulatio ns of a two fluid model are presented. To simulate physically reasonab le parameters in a tokamak geometry, an efficient approach is used in which only a narrow layer surrounding the q = 1 surface and m = 1 magn etic island must be simulated. In the usual tokamak case rho(s)>d(e), as well as the limit rho(s) = 0, the early nonlinear growth of the mod e is faster than exponential due a broadening of the flow layer. This broadening appears to result from tension in the magnetic field lines, which acts to pull the layer open as the island grows. (C) 1996 Ameri can Institute of Physics.