Wave Leakage and Resonant Absorption in a Loop Embedded in a Coronal Arcade

TL;DR

This study explores how wave leakage and resonant absorption affect oscillations in a coronal loop embedded in a potential arcade, revealing that perpendicular wave propagation enhances trapping and damping mechanisms.

Contribution

It introduces a model including wave propagation in the ignorable direction, demonstrating its impact on wave trapping and energy transfer in coronal loops.

Findings

Wave leakage damping is less effective with perpendicular propagation.

Perpendicular propagation enables resonant damping of vertical oscillations.

Energy transfer occurs from the loop interior to the external corona.

Abstract

We investigate the temporal evolution of impulsively generated perturbations in a potential coronal arcade with an embedded loop. As the initial configuration we consider a coronal loop, represented by a density enhancement, which is unbounded in the ignorable direction of the arcade. The linearized time-dependent magnetohydrodynamic equations have been numerically solved in field-aligned coordinates and the time evolution of the initial perturbations has been studied in the zero-beta approximation. For propagation constrained to the plane of the arcade, the considered initial perturbations do not excite trapped modes of the system. This weakness of the model is overcome by the inclusion of wave propagation in the ignorable direction. The inclusion of perpendicular propagation produces two main results. First, damping by wave leakage is less efficient because the loop is able to act as a wave trap of vertical oscillations. Second, the consideration of an inhomogeneous corona enables the resonant damping of vertical oscillations and the energy transfer from the interior of the loop to the external coronal medium.