Modelling the propagation of slow magneto-acoustic waves in a multi-stranded coronal loop

Abstract

We study the propagation properties of slow magneto-acoustic waves in a multi-thermal coronal loop using a 3D MHD model, for the first time. A bundle of 33 vertical cylinders, each of 100{\,}km radius, randomly distributed over a circular region of radius 1{\,}Mm is considered to represent the coronal loop. The slow waves are driven by perturbing the vertical velocity ($v_z$) at the base of the loop. We apply forward modelling to the simulation results to generate synthetic images in the coronal channels of SDO/AIA. Furthermore, we add appropriate data noise to enable direct comparison with the real observations. It is found that the synthetic images at the instrument resolution show non-cospatial features in different temperature channels in agreement with previous observations. Time-distance maps are constructed from the synthetic data to study the propagation properties. The results indicate that the oscillations are only visible in specific channels depending on the temperature range of plasma existing within the loop. Additionally, the propagation speed of slow waves is also found to be sensitive to the available temperature range. Overall, we propose that the cross-field thermal properties of coronal structures can be inferred using a combination of numerical simulations and observations of slow magneto-acoustic waves.