Direct Observation of Coronal Magnetic Fields by Vector Tomography of the Coronal Emission Line Polarizations

TL;DR

This study achieves the first direct 3D observation of the global coronal magnetic fields using vector tomography, combining polarization measurements and scalar tomography to improve understanding of solar magnetic structures.

Contribution

It introduces a novel vector tomographic inversion method for coronal magnetic fields using polarization data and compares results with MHD simulations, highlighting its utility and limitations.

Findings

Vector tomography provides a consistent 3D magnetic field model.

MHD simulations generally agree with the tomography results.

Discrepancies highlight areas for future improvement.

Abstract

This article presents the first direct "observation" of the global-scale, 3D coronal magnetic fields of Carrington Rotation (CR) Cycle 2112 using vector tomographic inversion techniques. The Vector tomographic inversion uses observational measurements of the Fe {\sc{xiii}} 10747 \AA\ Hanle effect polarization signals by the Coronal Multichannel Polarimeter (CoMP) and coronal density and temperature structures derived from scalar tomographic inversion of STEREO/EUVI coronal emission lines (CELs) intensity images as inputs to derive a coronal magnetic field model that best reproduces the observed polarization signals. While independent verifications of the vector tomography results cannot be performed, we compared the tomography inverted coronal magnetic fields with those constructed by MagnetoHydroDynamic (MHD) simulation based on observed photospheric magnetic fields of CR 2112 and 2113. We found that the MHD model for CR 2112 is qualitatively consistent with the tomography inverted result for most of the reconstruction domain except for a couple of regions. Particularly for one of the most noticeable exception region, we found that the MHD simulation for CR 2113 predicted a model that more closely resemble the vector tomography inverted magnetic fields. We discuss the utilities and limitations of the tomographic inversion technique, and present ideas for future developments.