Reflection Of Propagating Slow Magneto-acoustic Waves In Hot Coronal Loops : Multi-instrument Observations and Numerical Modelling

TL;DR

This study combines multi-instrument observations and numerical modeling to analyze reflecting slow magneto-acoustic waves in hot coronal loops, revealing their generation, propagation, reflection, and damping mechanisms.

Contribution

First report of reflecting slow waves in hot coronal loops observed simultaneously by XRT and AIA, supported by 2.5D MHD simulations confirming wave behavior and damping causes.

Findings

Wave appears after micro-flare at footpoint

Wave speed is comparable to local sound speed

Thermal conduction causes wave damping

Abstract

Slow MHD waves are important tools for understanding the coronal structures and dynamics. In this paper, we report a number of observations, from X-Ray Telescope (XRT) on board HINODE and SDO/AIA of reflecting longitudinal waves in hot coronal loops. To our knowledge, this is the first report of this kind as seen from the XRT and simultaneously with the AIA. The wave appears after a micro-flare occurs at one of the footpoints. We estimate the density and the temperature of the loop plasma by performing DEM analysis on the AIA image sequence. The estimated speed of propagation is comparable or lower than the local sound speed suggesting it to be a propagating slow wave. The intensity perturbation amplitudes, in every case, falls very rapidly as the perturbation moves along the loop and eventually vanishes after one or more reflections. To check the consistency of such reflection signatures with the obtained loop parameters, we perform a 2.5D MHD simulation, which uses the parameters obtained from our observation as inputs and performed forward modelling to synthesize AIA 94~\r{A} images. Analyzing the synthesized images, we obtain the same properties of the observables as for the real observation. From the analysis we conclude that a footpoint heating can generate slow wave which then reflects back and forth in the coronal loop before fading out. Our analysis on the simulated data shows that the main agent for this damping is the anisotropic thermal conduction.