A Model for Nonthermal Particle Acceleration in Relativistic Magnetic Reconnection

The past decade has seen an outstanding development of nonthermal particle acceleration in magnetic reconnection in magnetically-dominated systems, with clear signatures of power-law energy distributions as a common outcome of first principle kinetic simulations. Here we propose a model for investigating nonthermal particle acceleration in reconnection in a systematic approach. We show that particle energy distributions are well determined by particle injection, acceleration, and escape processes. Using a series of ab initio kinetic simulations, we accurately evaluate the energy- and time-dependent transport coefficients. The resulting spectral characteristics, including the spectral index, lower and upper bound of the power-law distribution, agree well with the simulation results.