A Magnetohydrodynamic Relaxation Method for Non-Force-Free Magnetic Field in Magnetohydrostatic Equilibrium

TL;DR

This paper introduces a magnetohydrodynamic relaxation method to reconstruct non-force-free magnetic fields in the solar atmosphere, accounting for pressure and gravity, improving upon traditional force-free models.

Contribution

The paper develops a new MHD relaxation approach that models the solar magnetic field in magnetohydrostatic equilibrium, including pressure and gravitational forces, which are ignored in previous NLFFF methods.

Findings

Successfully reconstructs magnetic fields with pressure and gravity effects.

Demonstrates robustness of the numerical solver in 2D experiments.

Provides a framework for more realistic solar magnetic field modeling.

Abstract

A nonlinear force-free field (NLFFF) extrapolation is widely used to reconstruct the three-dimensional magnetic field in the solar corona from the observed photospheric magnetic field. However, the pressure gradient and gravitational forces are ignored in the NLFFF model, even though the photospheric and chromospheric magnetic fields are not in general force-free. Here we develop a magnetohydrodynamic (MHD) relaxation method that reconstructs the solar atmospheric (chromospheric and coronal) magnetic field as a non-force-free magnetic field (NFFF) in magnetohydrostatic equilibrium where the Lorentz, pressure gradient, and gravitational forces are balanced. The system of basic equations for the MHD relaxation method is derived, and mathematical properties of the system are investigated. A robust numerical solver for the system is constructed based on the modern high-order shock capturing scheme. Two-dimensional numerical experiments that include the pressure gradient and gravitational forces are also demonstrated.