Ion larmor radius effects in collisionless reconnection

The nonlinear evolution of collisionless magnetic field line reconnection i s investigated numerically in plasma regimes where the effects of the elect ron and ion temperatures are important. These effects modify the structure of the current and vorticity layers that are formed during the onset of the reconnection instability. The results of investigations in a two-dimension al periodic configuration including ion Larmor radius effects to all orders are presented and compared with the results obtained in regimes with a lar ge sound Larmor radius. It is found that, while the roles of the sound Larm or radius and the ion Larmor radius are interchangeable as far as the nonli near reconnection rate is concerned, the structure of the vorticity and cur rent density layers is different in the two cases. (C) 2000 MAIK "Nauka/Int erperiodica".