Very High Order $\PNM$ Schemes on Unstructured Meshes for the Resistive Relativistic MHD Equations

TL;DR

This paper introduces the first high-order accurate numerical method for resistive relativistic MHD equations on unstructured meshes, capable of handling stiff source terms and complex shock phenomena in astrophysical simulations.

Contribution

It develops a novel high-order $ ext{PNM}$ scheme combined with a space-time DG approach for the first time applied to resistive relativistic MHD on unstructured meshes.

Findings

Achieves 3rd to 5th order accuracy in space and time.

Successfully handles stiff source terms and low resistivity regimes.

Accurately simulates shock waves and magnetic reconnection phenomena.

Abstract

In this paper we propose the first better than second order accurate method in space and time for the numerical solution of the resistive relativistic magnetohydrodynamics (RRMHD) equations on unstructured meshes in multiple space dimensions. The nonlinear system under consideration is purely hyperbolic and contains a source term, the one for the evolution of the electric field, that becomes stiff for low values of the resistivity. For the spatial discretization we propose to use high order $\PNM$ schemes as introduced in \cite{Dumbser2008} for hyperbolic conservation laws and a high order accurate unsplit time discretization is achieved using the element-local space-time discontinuous Galerkin approach proposed in \cite{DumbserEnauxToro} for one-dimensional balance laws with stiff source terms. The divergence free character of the magnetic field is accounted for through the divergence cleaning procedure of Dedner et al. \cite{Dedneretal}. To validate our high order method we first solve some numerical test cases for which exact analytical reference solutions are known and we also show numerical convergence studies in the stiff limit of the RRMHD equations using $\PNM$ schemes from third to fifth order of accuracy in space and time. We also present some applications with shock waves such as a classical shock tube problem with different values for the conductivity as well as a relativistic MHD rotor problem and the relativistic equivalent of the Orszag-Tang vortex problem. We have verified that the proposed method can handle equally well the resistive regime and the stiff limit of ideal relativistic MHD. For these reasons it provides a powerful tool for relativistic astrophysical simulations involving the appearance of magnetic reconnection.