  While a growing body of research indicates that relativistic magnetic
reconnection is a prodigious source of particle acceleration in high-energy
astrophysical systems, the dominant acceleration mechanism remains
controversial. Using a combination of fully kinetic simulations and theoretical
analysis, we demonstrate that Fermi-type acceleration within the large-scale
motional electric fields dominates over direct acceleration from non-ideal
electric fields within small-scale diffusion regions. This result has profound
implications for modeling particle acceleration in large-scale astrophysical
problems, since it opens up the possiblity of modeling the energetic spectra
without resolving microscopic diffusion regions.
