The resonant damping of fast magnetohydrodynamic oscillations in a system of two coronal slabs

TL;DR

This study investigates how resonant damping of MHD oscillations in coronal loops is affected by the interaction of two inhomogeneous slabs, revealing mode splitting, altered frequencies, and variable damping rates depending on slab separation and wave propagation angles.

Contribution

It provides a detailed analysis of resonant damping in a two-slab coronal loop system, extending single loop models to include interactions and mode splitting effects.

Findings

Normal modes split into symmetric and antisymmetric oscillations due to loop interaction.

Damping rates vary significantly with slab separation and wave propagation angle.

Surface-like oscillations experience strong damping, while sausage body-like modes are less affected.

Abstract

Observations of transversal coronal loop oscillations very often show the excitation and damping of oscillations in groups of coronal loops rather than in individual and isolated structures. We present results on the oscillatory properties (periods, damping rates, and spatial distribution of perturbations) for resonantly damped oscillations in a system of two inhomogeneous coronal slabs and compare them to the properties found in single slab loop models. A system of two identical coronal loops is modeled, in Cartesian geometry, as being composed by two density enhancements. The linear magnetohydrodynamic (MHD) wave equations for oblique propagation of waves are solved and the damping of the different solutions, due to the transversal inhomogeneity of the density profile, is computed. The physics of the obtained results is analyzed by an examination of the perturbed physical variables. We find that, due to the interaction between the loops, the normal modes of oscillation present in a single slab split into symmetric and antisymmetric oscillations when a system of two identical slabs is considered. The frequencies of these solutions may differ from the single slab results when the distance between the loops is of the order of a few slab widths. Oblique propagation of waves weakens this interaction, since solutions become more confined to the edges of the slabs. The damping is strong for surface-like oscillations, while sausage body-like solutions are unaffected. For some solutions, and small slab separations, the damping in a system of two loops differs substantially from the damping of a single loop.