The Effects of Sub-Relativistic Magnetization on Reconnection X-Point Particle Acceleration

Magnetic reconnection is a ubiquitous plasma process responsible for rapid and substantial magnetic energy dissipation throughout the universe. It is also a major candidate to explain the generation of large populations of nonthermal particles observed in a wide variety of environments. While simulations of relativistic reconnection have convincingly demonstrated its potential to generate hard power-laws, non-relativistic simulations have faced difficulty doing the same. To elucidate the physics responsible for this discrepancy, we perform 2D particle-in-cell simulations of magnetic reconnection using the Tristan v2 code. We contrast the dynamics of the non-relativistic regime (magnetization < 1) with the fully relativistic regime (magnetization >> 1) for pair plasmas, focusing on the x-points, critical injection sites for subsequent acceleration. We find that in the sub-relativistic case the smaller spatial extent of the diffusion regions is primarily responsible for suppressed nonthermal particle energization.