Parallel electric fields are inefficient drivers of energetic electrons   in magnetic reconnection
  We present two-dimensional kinetic simulations, with a broad range of initial guide fields, that isolate the role of parallel electric fields ($E_\parallel$) in energetic electron production during collisionless magnetic reconnection. In the strong guide field regime, $E_\parallel$ drives essentially all of the electron energy gain, yet fails to generate an energetic component. We suggest that this is due to the weak energy scaling of particle acceleration from $E_\parallel$ 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. 
J. T. Dahlin, J. F. Drake, M. Swisdak
physics.plasm-ph