Outflow Driven Particle Acceleration in 3D Magnetic Reconnection.

High-energy particle emissions remain one of the most captivating and least understood phenomena in the universe, as evidenced by nonthermal radiation from astrophysical systems. In this study, we employ kinetic simulations of 3D relativistic reconnection in the collisionless regime using the VPIC code to analyze particle acceleration mechanisms. We find that particle energization is primarily driven by Fermi acceleration through interactions with reconnection outflows, challenging previous findings that emphasized the role of inflow interactions. These results offer new insights into the mechanisms behind high-energy particle acceleration.