Comparison of damping mechanisms for transverse waves in solar coronal loops

TL;DR

This study uses Bayesian methods to evaluate different damping mechanisms for transverse waves in solar coronal loops, finding that no single mechanism is conclusively dominant across all observed cases.

Contribution

It introduces a Bayesian framework to compare the plausibility of various damping mechanisms in solar coronal loops based on observational data.

Findings

Resonant absorption and wave leakage are plausible in strong damping cases.

Phase mixing is favored for weak/moderate damping.

Limited cases show strong evidence for a specific damping mechanism.

Abstract

We present a method to assess the plausibility of alternative mechanisms to explain the damping of magnetohydrodynamic (MHD) transverse waves in solar coronal loops. The considered mechanisms are resonant absorption of kink waves in the Alfv\'en continuum, phase-mixing of Alfv\'en waves, and wave leakage. Our methods make use of Bayesian inference and model comparison techniques. We first infer the values for the physical parameters that control the wave damping, under the assumption of a particular mechanism, for typically observed damping time-scales. Then, the computation of marginal likelihoods and Bayes factors enable us to quantify the relative plausibility between the alternative mechanisms. We find that, in general, the evidence is not large enough to support a single particular damping mechanism as the most plausible one. Resonant absorption and wave leakage offer the most probable explanations in strong damping regimes, while phase mixing is the best candidate for weak/moderate damping. When applied to a selection of 89 observed transverse loop oscillations, with their corresponding measurements of damping times scales and taking into account data uncertainties, we find that only in a few cases positive evidence for a given damping mechanism is available.