An MHD Study of Large-Amplitude Oscillations in Solar Filaments

TL;DR

This study uses 2.5D MHD simulations to analyze how large-scale coronal shock waves can excite and influence oscillations in solar filaments, revealing dependencies on filament parameters and the dominant restoring force.

Contribution

It provides a novel simulation-based analysis of filament oscillations triggered by coronal shocks, detailing the effects of various filament parameters on oscillation characteristics.

Findings

Oscillation periods increase with filament height.

Larger filaments have shorter periods and smaller amplitudes.

Magnetic tension is the main restoring force.

Abstract

Quiescent filaments are usually affected by internal and/or external perturbations triggering oscillations of different kinds. In particular, external large-scale coronal waves can perturb remote quiescent filaments leading to large-amplitude oscillations. Observational reports have indicated that the activation time of oscillations coincides with the passage of a large-scale coronal wavefront through the filament, although the disturbing wave is not always easily detected. Aiming to contribute to understand how -- and to what extent -- coronal waves are able to excite filament oscillations, here we modelled with 2.5 MHD simulations a filament floating in a gravitationally stratified corona disturbed by a coronal shock wave. This simplified scenario results in a two-coupled oscillation pattern of the filament which is damped in a few cycles, enabling a detailed analysis. A parametric study was accomplished varying parameters of the scenario such as height, size and mass of the filament. An oscillatory analysis reveals a general tendency where periods of oscillations, amplitudes and damping times increase with height, whereas filaments of larger radius exhibit shorter periods and smaller amplitudes. The calculation of forces exerted on the filament shows that the main restoring force is the magnetic tension.