An MHD study of large-amplitude oscillations in solar filaments

Abstract

Quiescent filaments are usually affected by internal and/or externalperturbations 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 understanding how ?and to what extent? coronal waves are able to excite filament oscillations, here we modelled with 2.5D MHD simulations a filament floating in a gravitationally stratified corona disturbed by acoronal shock wave. This simplified scenario results in a two-coupled-oscillation pattern of the filament, which is damped in a few cycles, enabling a detailedanalysis. A parametric study was carried out varying parameters of the scenario such as height, size, and mass of the filament. An oscillatory analysis reveals a general tendency for periods of oscillations, amplitudes, and damping times to increase with height, whereas filaments of larger radius exhibit shorter periods and smaller amplitudes. The calculation of forces exerted on the filament showsthat the main restoring force is the magnetic tension.