Hanle Effect Diagnostics of the Coronal Magnetic Field - A Test Using Realistic Magnetic Field Configurations

TL;DR

This study evaluates the potential of the Hanle effect in UV spectral lines, especially H I Lyβ, for diagnosing the coronal magnetic field using realistic magnetic field models.

Contribution

It demonstrates the diagnostic potential of UV Hanle effect measurements, particularly H I Lyβ, for probing the coronal magnetic field with realistic magnetic configurations.

Findings

H I Lyβ is particularly useful for magnetic field diagnostics.

The Hanle effect signals can be detected outside the solar limb.

Magnetic field extrapolations help assess diagnostic capabilities.

Abstract

Our understanding of coronal phenomena, such as coronal plasma thermodynamics, faces a major handicap caused by missing coronal magnetic field measurements. Several lines in the UV wavelength range present suitable sensitivity to determine the coronal magnetic field via the Hanle effect. The latter is a largely unexplored diagnostic of coronal magnetic fields with a very high potential. Here we study the magnitude of the Hanle-effect signal to be expected outside the solar limb due to the Hanle effect in polarized radiation from the H {\sc{i}} Ly$\alpha$ and $\beta$ lines, which are among the brightest lines in the off-limb coronal FUV spectrum. For this purpose we use a magnetic field structure obtained by extrapolating the magnetic field starting from photospheric magnetograms. The diagnostic potential of these lines for determining the coronal magnetic field, as well as their limitations are studied. We show that these lines, in particular H {\sc{i}} Ly$\beta$, are useful for such measurements.