Energy Gain from Nonideal Electric Fields During Injection in Relativistic Magnetic Reconnection

Magnetic reconnection is a ubiquitous plasma process that mediates the transfer of energy from magnetic fields to particles in magnetized plasmas. It is believed to be an important source of nonthermal energetic particles in systems ranging from astrophysical compact objects to laboratory fusion devices. The large separation of global and microscopic scales involved in reconnection makes it challenging to model with high resolution, and thus it is critical to determine which reduced physical models are capable of accurately modeling particle acceleration from reconnection. By resolving the energy gain from ideal and nonideal magnetohydrodynamic electric fields self-consistently within kinetic particle- in-cell simulations of reconnection, we find that the nonideal fields play a dominant role in the early stage of energization known as injection. Simulations with different initial conditions show that the importance of the nonideal field increases with magnetization, guide field, and in three-dimensions, indicating its general importance for reconnection in natural astrophysical systems. The statistical properties of the injection process can be obtained from the simulations, which may potentially enable the future development of extended fluid models capable of accurately modeling particle acceleration in large-scale systems. The analysis method presented can be applied more broadly to give new insight into magnetized plasma systems ranging from astrophysics to the laboratory.