Particle Injection and Nonthermal Particle Acceleration in Relativistic Magnetic Reconnection*

Magnetic reconnection in the relativistic regime has been proposed as an important process for efficient production of nonthermal particles and high-energy emissions. Using fully kinetic particle-in-cell simulations, we investigate how guide-field strength domain size affect characteristic spectral features acceleration processes. We study two stages acceleration: energization up until injection energy $\gamma_{\rm inj}$ further that generates a power-law spectrum. Stronger guide fields increase index inj}$, which suppresses efficiency. These quantities seemingly converge with increasing size, suggesting our findings can be extended to large-scale systems. find three distinct mechanisms contribute during injection: particle streaming along parallel electric field, Fermi reflection, pickup process. processes, related field perpendicular magnetic govern weak larger domains. Meanwhile, are strong regime. In post-injection stage, dominate regime, whereas control fields. will help explain emissions astrophysics, including black hole jets pulsar wind nebulae.