Formation of a localized acceleration potential during magnetic reconnection with a guide field

Magnetic reconnection near the surface of the sun and in the Earth’s magnetotail is associated with the production of highly energetic electrons. Direct acceleration in the reconnection electric field has been proposed as a possible mechanism for energizing these electrons. Here, however, we use kinetic simulations of guide-field reconnection to show that in two-dimensional (2D) reconnection the parallel electric field, E∥ in the reconnection region is localized and its structure does not permit significant energization of the electrons. Rather, a large fraction of the electrons become trapped due to a sign reversal in E∥, imposing strict constraints on their motions and energizations. Given these new results, simple 2D models, which invoke direct acceleration for energizing electrons during a single encounter with a reconnection region, need to be revised.