Observational evidence of resonantly damped propagating kink waves in the solar corona

TL;DR

This paper provides observational evidence that resonant absorption causes damping of propagating kink waves in the solar corona, supporting theoretical models and revealing the plasma inhomogeneity's role as a natural filter.

Contribution

It demonstrates the frequency-dependent damping of kink waves in the corona, confirming the resonant absorption mechanism through novel CoMP observations and theoretical interpretation.

Findings

Kink waves exhibit frequency-dependent damping lengths up to 8 mHz.

Observed damping behavior aligns with resonant absorption theory.

Transverse plasma inhomogeneity parameters match previous TRACE observations.

Abstract

In this Letter we establish clear evidence for the resonant absorption damping mechanism by analyzing observational data from the novel Coronal Multi-Channel Polarimeter (CoMP). This instrument has established that in the solar corona there are ubiquitous propagating low amplitude ($\approx$1 km s$^{-1}$) Alfv\'{e}nic waves with a wide range of frequencies. Realistically interpreting these waves as the kink mode from magnetohydrodynamic (MHD) wave theory, they should exhibit a frequency dependent damping length due to resonant absorption, governed by the TGV relation showing that transversal plasma inhomogeneity in coronal magnetic flux tubes causes them to act as natural low-pass filters. It is found that observed frequency dependence on damping length (up to about 8 mHz) can be explained by the kink wave interpretation and furthermore, the spatially averaged equilibrium parameter describing the length scale of transverse plasma density inhomogeneity over a system of coronal loops is consistent with the range of values estimated from TRACE observations of standing kink modes.