How to use magnetic field information for coronal loop identification?

TL;DR

This paper explores using magnetic field extrapolation from photospheric data to identify coronal loops by comparing reconstructed magnetic field lines with plasma emission structures in solar images.

Contribution

It introduces a method to identify coronal loops by projecting magnetic field extrapolations onto EIT images and analyzing emissivity gradients along magnetic field lines.

Findings

Magnetic field extrapolation helps locate coronal loops.

Coronal loops are identified as closed magnetic field lines with high emissivity.

The method improves understanding of coronal magnetic structures.

Abstract

The structure of the solar corona is dominated by the magnetic field because the magnetic pressure is about four orders of magnitude higher than the plasma pressure. Due to the high conductivity the emitting coronal plasma (visible e.g. in SOHO/EIT) outlines the magnetic field lines. The gradient of the emitting plasma structures is significantly lower parallel to the magnetic field lines than in the perpendicular direction. Consequently information regarding the coronal magnetic field can be used for the interpretation of coronal plasma structures. We extrapolate the coronal magnetic field from photospheric magnetic field measurements into the corona. The extrapolation method depends on assumptions regarding coronal currents, e.g. potential fields (current free) or force-free fields (current parallel to magnetic field). As a next step we project the reconstructed 3D magnetic field lines on an EIT-image and compare with the emitting plasma structures. Coronal loops are identified as closed magnetic field lines with a high emissivity in EIT and a small gradient of the emissivity along the magnetic field.