Frequency-dependent damping in propagating slow magneto-acoustic waves

TL;DR

This study investigates the frequency-dependent damping of slow magneto-acoustic waves in solar structures, revealing discrepancies with existing theories and differences between polar and on-disk observations.

Contribution

It introduces a new analysis method to quantify the relation between damping length and frequency from observational data.

Findings

Damping length varies with wave frequency in observed solar structures.

Observed frequency dependence differs from current linear wave theory.

Polar and on-disk structures exhibit different damping behaviors.

Abstract

Propagating slow magneto-acoustic waves are often observed in polar plumes and active region fan loops. The observed periodicities of these waves range from a few minutes to few tens of minutes and their amplitudes were found to decay rapidly as they travel along the supporting structure. Previously, thermal conduction, compressive viscosity, radiation, density stratification, and area divergence, were identified to be some of the causes for change in the slow wave amplitude. Our recent studies indicate that the observed damping in these waves is frequency dependent. We used imaging data from SDO/AIA, to study this dependence in detail and for the first time from observations we attempted to deduce a quantitative relation between damping length and frequency of these oscillations. We developed a new analysis method to obtain this relation. The observed frequency dependence does not seem to agree with the current linear wave theory and it was found that the waves observed in the polar regions show a different dependence from those observed in the on-disk loop structures despite the similarity in their properties.