Energy conversion and scaling analysis of relativistic magnetic reconnection

Abstract

Relativistic magnetic reconnection is a key process for accelerating charged particles and producing high-energy radiation. We study this process using relativistic resistive magnetohydrodynamics simulations. Starting with Harris sheet configuration, we study time evolution of reconnection rate and the Alfven four Mach number for outflow. These measurements validate the Sweet-Parker scaling, consistent with previous studies. To study energy conversion processes, we calculate Ohmic dissipation, crucial for understanding how energy is converted between plasma and electromagnetic fields. Decomposing electric field components relative to velocity field, we find that energy conversion is initially dominated by the resistive electric field, but convective electric fields take over as reconnection progresses. Plasma primarily gains energy within the current sheet and near the separatrix. We perform a scan of magnetization for mildly relativistic plasma to examine scaling laws previously derived for non-relativistic inflow. We find the inflow is slower than predicted, due to conversion of magnetic energy mostly into thermal energy, causing strong compressibility. We calculate and verify the scaling of the compressibility factor, providing a more accurate representation of inflow dynamics. We analyze the impact of a guide field on reconnection and energy partition, finding that a stronger guide field reduces the reconnection rate but has minimal effect on the relative distribution of kinetic, magnetic, and thermal energy. Addition of rotating guide field and variations in initial pressure and density have little effect on the energy composition of the outflow, with thermal energy consistently dominating at nearly 90%.