Spatial Damping of Propagating Kink Waves in Prominence Threads

TL;DR

This paper investigates how resonant absorption and ion-neutral collisions damp propagating kink waves in solar prominence threads, providing analytical and numerical insights into their roles and implications for prominence seismology.

Contribution

It offers a detailed analysis of the damping mechanisms of kink waves in prominence threads, highlighting the dominance of resonant absorption over ion-neutral collisions for observed periods.

Findings

Resonant absorption efficiently damps kink waves at typical oscillation periods.

Ion-neutral collisions have a minor damping effect at observed periods.

Resonant absorption can explain the observed spatial damping of kink waves.

Abstract

Transverse oscillations and propagating waves are frequently observed in threads of solar prominences/filaments and have been interpreted as kink magnetohydrodynamic (MHD) modes. We investigate the spatial damping of propagating kink MHD waves in transversely nonuniform and partially ionized prominence threads. Resonant absorption and ion-neutral collisions (Cowling's diffusion) are the damping mechanisms taken into account. The dispersion relation of resonant kink waves in a partially ionized magnetic flux tube is numerically solved by considering prominence conditions. Analytical expressions of the wavelength and damping length as functions of the kink mode frequency are obtained in the Thin Tube and Thin Boundary approximations. For typically reported periods of thread oscillations, resonant absorption is an efficient mechanism for the kink mode spatial damping, while ion-neutral collisions have a minor role. Cowling's diffusion dominates both the propagation and damping for periods much shorter than those observed. Resonant absorption may explain the observed spatial damping of kink waves in prominence threads. The transverse inhomogeneity length scale of the threads can be estimated by comparing the observed wavelengths and damping lengths with the theoretically predicted values. However, the ignorance of the form of the density profile in the transversely nonuniform layer introduces inaccuracies in the determination of the inhomogeneity length scale.