On the magnetism and dynamics of prominence legs hosting tornadoes

TL;DR

This paper investigates the magnetic structure and dynamics of solar prominence legs hosting tornadoes, revealing smooth magnetic fields, vertical helical structures, and oscillatory or intermittent rotational motions.

Contribution

It provides new spectropolarimetric evidence showing prominence legs have vertical helical magnetic fields and clarifies the nature of their apparent rotation as oscillations or intermittent rotation.

Findings

Magnetic fields in prominences are very smooth.

Prominence legs exhibit vertical helical magnetic structures.

Observed velocity patterns are consistent with oscillations or short-lived rotations.

Abstract

Solar tornadoes are dark vertical filamentary structures observed in the extreme ultraviolet associated with prominence legs and filament barbs. Their true nature and relationship to prominences requires understanding their magnetic structure and dynamic properties. Recently, a controversy has arisen: is the magnetic field organized forming vertical, helical structures or is it dominantly horizontal? And concerning their dynamics, are tornadoes really rotating or is it just a visual illusion? Here, we analyze four consecutive spectropolarimetric scans of a prominence hosting tornadoes on its legs which help us shed some light on their magnetic and dynamical properties. We show that the magnetic field is very smooth in all the prominence, probably an intrinsic property of the coronal field. The prominence legs have vertical helical fields that show slow temporal variation probably related to the motion of the fibrils. Concerning the dynamics, we argue that 1) if rotation exists, it is intermittent, lasting no more than one hour, and 2) the observed velocity pattern is also consistent with an oscillatory velocity pattern (waves).