Observational Test of Coronal Magnetic Field Models I. Comparison with Potential Field Model

TL;DR

This study compares observed coronal magnetic field maps with potential field models, providing evidence that potential field extrapolations can reasonably approximate the magnetic structure of stable active regions in the solar corona.

Contribution

It offers the first observational validation of potential field models for the solar corona using spectropolarimetric data of an active region.

Findings

Potential field models agree with observations near the sunspot

Reasonable approximation for simple, stable active regions

First direct observational validation of potential field extrapolation

Abstract

Recent advances have made it possible to obtain two-dimensional line-of-sight magnetic field maps of the solar corona from spectropolarimetric observations of the Fe XIII 1075 nm forbidden coronal emission line. Together with the linear polarization measurements that map the azimuthal direction of the coronal magnetic field, these coronal vector magnetograms now allow for direct observational testing of theoretical coronal magnetic field models. This paper presents a study testing the validity of potential-field coronal magnetic field models. We constructed a theoretical coronal magnetic field model of active region AR 10582 observed by the SOLARC coronagraph in 2004 by a global potential field extrapolation of the synoptic map of Carrington Rotation 2014. Synthesized linear and circular polarization maps from thin layers of the coronal magnetic field model above the active region along the line of sight are compared with the observed maps. We found that reasonable agreement occurs from layers located just above the sunspot of AR 10582, near the plane of the sky. This result provides the first observational evidence that potential field extrapolation can yield a reasonable approximation of the magnetic field configuration of the solar corona for simple and stable active regions.