Magnetic field in atypical prominence structures: Bubble, tornado and eruption

TL;DR

This study investigates the magnetic field configurations in atypical solar prominences like tornadoes, bubbles, and eruptions using spectropolarimetric data, revealing diverse magnetic orientations and strengths that challenge simpler models.

Contribution

It provides detailed magnetic field measurements in atypical prominences and highlights the complexity and possible turbulence of magnetic fields in these structures.

Findings

Magnetic field in tornadoes is mostly horizontal.

Eruptive prominences have predominantly vertical magnetic fields.

Higher magnetic field strength observed inside bubbles.

Abstract

Spectropolarimetric observations of prominences have been obtained with the THEMIS telescope during four years of coordinated campaigns. Our aim is now to understand the conditions of the cool plasma and magnetism in `atypical' prominences, namely when the measured inclination of the magnetic field departs, to some extent, from the predominantly horizontal field found in `typical' prominences. What is the role of the magnetic field in these prominence types? Are plasma dynamics more important in these cases than the magnetic support? We focus our study on three types of `atypical' prominences (tornadoes, bubbles and jet-like prominence eruptions) that have all been observed by THEMIS in the He I D_3 line, from which the Stokes parameters can be derived. The magnetic field strength, inclination and azimuth in each pixel are obtained by using the Principal Component Analysis inversion method on a model of single scattering in the presence of the Hanle effect. The magnetic field in tornadoes is found to be more or less horizontal, whereas for the eruptive prominence it is mostly vertical. We estimate a tendency towards higher values of magnetic field strength inside the bubbles than outside in the surrounding prominence. In all of the models in our database, only one magnetic field orientation is considered for each pixel. While sufficient for most of the main prominence body, this assumption appears to be oversimplified in atypical prominence structures. We should consider these observations as the result of superposition of multiple magnetic fields, possibly even with a turbulent field component.