Parallel electric fields are inefficient drivers of energetic electrons in magnetic reconnection

Abstract

We present two-dimensional kinetic simulations, with a broad range of initial guide fields, which isolate the role of parallel electric fields (E∥) in energetic electron production during collisionless magnetic reconnection. In the strong guide field regime, E∥ drives essentially all of the electron energy gains, yet fails to generate an energetic component. We suggest that this is due to the weak energy scaling of particle acceleration from E∥ compared to that of a Fermi-type mechanism responsible for energetic electron production in the weak guide-field regime. This result has important implications for energetic electron production in astrophysical systems and reconnection-driven dissipation in turbulence.