Observed damping of the slow magnetoacoustic mode

TL;DR

This study measures the decay length of slow magnetoacoustic waves in coronal loops and finds magnetic field divergence as the primary damping mechanism, providing constraints for solar coronal wave models.

Contribution

It offers the first three-dimensional measurement of the decay length and density profile of slow magnetoacoustic waves in coronal loops, highlighting magnetic divergence as the key damping factor.

Findings

Decay length scale of ~20,000 km for slow waves

Uniform density profile along the loop base

Magnetic field divergence dominates damping

Abstract

Spectroscopic and stereoscopic imaging observations of slow magnetoacoustic wave propagation within a coronal loop are investigated to determine the decay length scale of the slow magnetoacoustic mode in three dimensions and the density profile within the loop system. The slow wave is found to have an e-folding decay length scale of $20,000^{+4000}_{-3000}$km with a uniform density profile along the loop base. These observations place quantitive constraints on the modelling of wave propagation within coronal loops. Theoretical forward modelling suggests that magnetic field line divergence is the dominant damping factor and thermal conduction is insufficient, given the observed parameters of the coronal loop temperature, density and wave mode period.