Transverse oscillations of a double-structured solar filament^⋆

¹ University of South Bohemia, Faculty of Science, Institute of Physics, Branišovská 1760, 370 05 České Budějovice, Czech Republic
e-mail: pjelinek@prf.jcu.cz
² Astronomical Institute of the Czech Academy of Sciences, Fričova 258, 251 65 Ondřejov, Czech Republic
³ Central (Pulkovo) Astronomical Observatory, Russian Academy of Sciences, Pulkovskoe Shausse 65, 196140 St. Petersburg, Russia
⁴ Crimean Astrophysical Observatory of the Russian Academy of Sciences Nauchny Russia, Russia

Received: 3 October 2019
Accepted: 27 March 2020

Abstract

Aims. We study the transverse oscillations of a double-structured solar filament.

Methods. We modelled the filament numerically via a 2D magnetohydrodynamic (MHD) model, in which we solved a full set of time-dependent MHD equations by means of the FLASH code, using the adaptive mesh refinement method. We used the wavelet analysis method as a diagnostic tool for analysing periods in simulated oscillations.

Results. We present a model of a solar filament combined with semi-empirical C7 model of the quiet solar atmosphere. This model is an alternative model of a filament based on the magnetostatic solution of MHD equations. We find that this double-structured filament oscillates with two different eigen frequencies. The ratio is approximately 1.75 (∼7.4 min/∼4.2 min), which is characteristic for this type of filament model. To show the details of these oscillations we present a time evolution of the plasma density, temperature, plasma beta parameter, and the ratio of gravity to magnetic pressure taken along the vertical axis of the filament at x = 0. The periods found by numerical simulations are then discussed in comparison with those observed.