Collisionless magnetic reconnection in asymmetric magnetic reconnection : hybrid and fully kinetic simulations

Magnetic reconnection in collisionless environments is thought to be controlled by the Hall effect, and thus be adequately modeled by any formalism including this electron-ion inertial decoupling. Recent work however suggest that the electron physics and the dissipation region in the vicinity of the reconnection site is playing a key role in controlling the process. In this work, we have revisited the topic of the role of the electron physics in the context of collisionless reconnection occurring in asymmetric tangential current layers, where the density profile and the magnetic profile are both asymmetric, and possibly including a guide field. Using two dimensional hybrid simulations with different non-ideal mechanisms, we find, contrary to what is observed in symmetric configurations, that neglecting the viscous mechanism occurring at the X line in asymmetric systems, results in a highly unsteady process with elongated electron current sheets producing plasmoids. Comparisons between hybrid+hyper-resistivity and fully kinetic PIC simulations however reveal striking similarities of ion scale features. Both coplanar and non-coplanar cases are discussed.