An Extension of the Athena++ Code Framework for GRMHD Based on Advanced Riemann Solvers and Staggered-Mesh Constrained Transport

TL;DR

This paper introduces an enhanced GRMHD code within Athena++ that utilizes advanced Riemann solvers and a staggered-mesh constrained transport method, improving accuracy and flexibility for simulations in curved spacetimes.

Contribution

The paper presents a new GRMHD code with advanced Riemann solvers and a staggered-mesh constrained transport algorithm, enabling accurate divergence-free magnetic fields in arbitrary stationary spacetimes.

Findings

Reliable performance in various tests

Enhanced accuracy with advanced Riemann solvers

Good scalability and efficiency

Abstract

We present a new general relativistic magnetohydrodynamics (GRMHD) code integrated into the Athena++ framework. Improving upon the techniques used in most GRMHD codes, ours allows the use of advanced, less diffusive Riemann solvers, in particular HLLC and HLLD. We also employ a staggered-mesh constrained transport algorithm suited for curvilinear coordinate systems in order to maintain the divergence-free constraint of the magnetic field. Our code is designed to work with arbitrary stationary spacetimes in one, two, or three dimensions, and we demonstrate its reliability in a number of tests. We also report on its promising performance and scalability.