Large Amplitude Longitudinal Oscillations in a Solar Filament

TL;DR

This paper presents a self-consistent model explaining large-amplitude longitudinal oscillations in solar filaments, identifying gravity as the restoring force and thermal processes as damping mechanisms, with implications for magnetic field diagnostics.

Contribution

The study introduces the first comprehensive model linking observed filament oscillations with magnetic and thermal processes, providing a new seismological tool for coronal magnetic field estimation.

Findings

Oscillation period is independent of tube length and mass growth.

Damping is caused by steady mass accretion onto threads.

Model supports sheared-arcade magnetic structure for filaments.

Abstract

We have developed the first self-consistent model for the observed large-amplitude oscillations along filament axes that explains the restoring force and damping mechanism. We have investigated the oscillations of multiple threads formed in long, dipped flux tubes through the thermal nonequilibrium process, and found that the oscillation properties predicted by our simulations agree with the observed behavior. We then constructed a model for the large-amplitude longitudinal oscillations that demonstrates that the restoring force is the projected gravity in the tube where the threads oscillate. Although the period is independent of the tube length and the constantly growing mass, the motions are strongly damped by the steady accretion of mass onto the threads by thermal nonequilibrium. The observations and our model suggest that a nearby impulsive event drives the existing prominence threads along their supporting tubes, away from the heating deposition site, without destroying them. The subsequent oscillations occur because the displaced threads reside in magnetic concavities with large radii of curvature. Our model yields a powerful seismological method for constraining the coronal magnetic field and radius of curvature of dips. Furthermore, these results indicate that the magnetic structure is most consistent with the sheared-arcade model for filament channels.