Magnetic Reconnection in 3D vs. 2D and Dependence on Magnetic Shear

Magnetic reconnection plays a central role for heating the solar coronal plasma including during flares as well as other places in the heliosphere and beyond, where each event can be characterized by its geometry and magnetic configurations, forming structures that we can categorize to be more 2D or 3D. The difference in reconnection rate between 2D and 3D simulations have been reported in multiple studies over the years. We report on a study of the reconnection rate using the resistive MHD code LaRe3D. We show that the rate depends strongly on the existence and interaction of different tearing layers (oblique tearing modes) within the current sheet. Such modes are only present with a finite guide field and a spatial dependence in this third direction. We find, as have others, that reconnection rates are artificially high in 2D simulations, and we offer an explanation.