Swaying threads of a solar filament

TL;DR

This paper reports high-resolution observations of oscillating solar filament threads, interprets these as kink magnetohydrodynamic waves, and estimates the magnetic field strength and Alfvén speed using seismological methods.

Contribution

It provides the first detailed observational evidence of kink MHD waves in solar filament threads and uses these observations for seismological estimations of magnetic parameters.

Findings

Detection of swaying motions in filament threads

Oscillations consistent with kink MHD waves

Estimated magnetic field strength and Alfvén speed

Abstract

From recent high resolution observations obtained with the Swedish 1 m Solar Telescope in La Palma, we detect swaying motions of individual filament threads in the plane of the sky. The oscillatory character of these motions are comparable with oscillatory Doppler signals obtained from corresponding filament threads. Simultaneous recordings of motions in the line of sight and in the plane of the sky give information about the orientation of the oscillatory plane. These oscillations are interpreted in the context of the magnetohydrodynamic theory. Kink magnetohydrodynamic waves supported by the thread body are proposed as an explanation of the observed thread oscillations. On the basis of this interpretation and by means of seismological arguments, we give an estimation of the thread Alfv\'en speed and magnetic field strength by means of seismological arguments.