Ion Larmor radius effects in collisionless reconnection

The nonlinear evolution of collisionless magnetic field line reconnection is investigated numerically in plasma regimes where the effects of the electron 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-dimensional periodic configuration including ion Larmor radius effects to all orders are presented and compared with the results obtained in regimes with a large sound Larmor radius. It is found that, while the roles of the sound Larmor radius and the ion Larmor radius are interchangeable as far as the nonlinear reconnection rate is concerned, the structure of the vorticity and current density layers is different in the two cases.