Magnetohydrodynamic kink waves in two-dimensional non-uniform prominence threads

TL;DR

This study investigates how longitudinal density structuring affects the oscillation periods and damping times of kink waves in prominence threads, providing insights into prominence seismology and plasma heating.

Contribution

It introduces a detailed 2D model of prominence threads with non-uniform density, analyzing the impact on kink wave damping and periods using resistive MHD equations.

Findings

Both thread length and evacuated part density significantly affect oscillation periods.

Damping times are strongly influenced by longitudinal density structuring.

Analysis explains the damping mechanisms via energy flux into resonances.

Abstract

We analyse the oscillatory properties of resonantly damped transverse kink oscillations in two-dimensional prominence threads. The fine structures are modelled as cylindrically symmetric magnetic flux tubes with a dense central part with prominence plasma properties and an evacuated part, both surrounded by coronal plasma. The equilibrium density is allowed to vary non-uniformly in both the transverse and the longitudinal directions.We examine the influence of longitudinal density structuring on periods, damping times, and damping rates for transverse kink modes computed by numerically solving the linear resistive magnetohydrodynamic (MHD) equations. The relevant parameters are the length of the thread and the density in the evacuated part of the tube, two quantities that are difficult to directly estimate from observations. We find that both of them strongly influence the oscillatory periods and damping times, and to a lesser extent the damping ratios. The analysis of the spatial distribution of perturbations and of the energy flux into the resonances allows us to explain the obtained damping times. Implications for prominence seismology, the physics of resonantly damped kink modes in two-dimensional magnetic flux tubes, and the heating of prominence plasmas are discussed.