A New Code for Nonlinear Force-Free Field Extrapolation of the Global Corona

TL;DR

This paper introduces a high-performance, parallelized global NLFFF extrapolation code for the solar corona, utilizing a magnetohydrodynamics relaxation approach and Yin-Yang grid to improve accuracy and efficiency in modeling the coronal magnetic field.

Contribution

It presents a novel parallelized global NLFFF extrapolation code based on MHD relaxation and Yin-Yang grid, suitable for high-resolution full-sphere magnetogram data.

Findings

Code validated with semi-analytic solutions showing high accuracy.

Demonstrates fast convergence and readiness for practical applications.

Potential for integration with adaptive mesh refinement techniques.

Abstract

Reliable measurements of the solar magnetic field are still restricted to the photosphere, and our present knowledge of the three-dimensional coronal magnetic field is largely based on extrapolation from photospheric magnetogram using physical models, e.g., the nonlinear force-free field (NLFFF) model as usually adopted. Most of the currently available NLFFF codes have been developed with computational volume like Cartesian box or spherical wedge while a global full-sphere extrapolation is still under developing. A high-performance global extrapolation code is in particular urgently needed considering that Solar Dynamics Observatory (SDO) can provide full-disk magnetogram with resolution up to $4096\times 4096$. In this work, we present a new parallelized code for global NLFFF extrapolation with the photosphere magnetogram as input. The method is based on magnetohydrodynamics relaxation approach, the CESE-MHD numerical scheme and a Yin-Yang spherical grid that is used to overcome the polar problems of the standard spherical grid. The code is validated by two full-sphere force-free solutions from Low & Lou's semi-analytic force-free field model. The code shows high accuracy and fast convergence, and can be ready for future practical application if combined with an adaptive mesh refinement technique.