Collisionless reconnection in instabilities and due to external forcing

Collisionless magnetic reconnection due to electron inertia is numerically investigated in two-dimensional, externally forced systems and unstable configurations. A common characteristic of reconnection in the two cases, associated with the effects of electron inertia and temperature, is a faster than exponential scale collapse. This collapse creates structures that are much narrower than the inertial reconnection layer, such as a very localized, X-shaped current distribution. The nonlinear evolution at this small scale is largely independent of large scale features such as the initial and boundary conditions which constitute the differences between driven and unstable cases. However, only in forced reconnection cases ion viscosity is found to stop the scale collapse of the current. High numerical resolution made the detailed investigation of small scale structure formation and continued scale collapse possible