Application of mesh refinement to relativistic magnetic reconnection

TL;DR

This paper demonstrates how mesh refinement techniques, combined with advanced solvers and absorbing layers, can efficiently simulate relativistic magnetic reconnection in 2D, reducing computational costs while maintaining accuracy.

Contribution

The study introduces modified mesh refinement algorithms and the use of PSATD solvers to improve simulation accuracy and efficiency in relativistic magnetic reconnection models.

Findings

Achieved good agreement with high-resolution simulations using only 36% of particles.

Reduced computational node-hours by 29% compared to baseline.

Validated mesh refinement methods for potential extension to 3D simulations.

Abstract

During relativistic magnetic reconnection, antiparallel magnetic fields undergo a rapid change in topology, releasing a large amount of energy in the form of non-thermal particle acceleration. This work explores the application of mesh refinement to 2D reconnection simulations to efficiently model the ineherent disparity in length-scales. We have systematically investigated the effects of mesh refinement and determined necessary modifications to the algorithm required to mitigate non-physical artifacts at the coarse-fine interface. We have used the ultrahigh-order Pseudo-Spectral Analytical Time-Domain (PSATD) Maxwell solver to analyze how its use can mitigate the numerical dispersion that occurs with the finite-difference time-domain (FDTD) (or ``Yee'') method. Absorbing layers are introduced at the coarse-fine interface to eliminate spurious effects that occur with mesh refinement. We also study how damping the electromagnetic fields and current density in the absorbing layer can help prevent the non-physical accumulation of charge and current density at the coarse-fine interface. Using a mesh refinement ratio of 8 for two-dimensional magnetic reconnection simulations, we obtained good agreement with the high resolution baseline simulation, using only 36% of the macroparticles and 71% of the node-hours needed for the baseline. The methods presented here are especially applicable to 3D systems where higher memory savings are expected than in 2D, enabling comprehensive, computationally efficient 3D reconnection studies in the future.