Large-Amplitude Longitudinal Oscillations Triggered by the Merging of Two Solar Filaments: Observations and Magnetic Field Analysis

Abstract

We follow the eruption of two related intermediate filaments observed in H$\alpha$ (from GONG) and in EUV (from SDO/AIA) and the resulting large-amplitude longitudinal oscillations of the plasma in the filament channels. The events occurred in and around the decayed active region AR12486 on 2016 January 26. Our detailed study of the oscillation reveals that the periods of the oscillations are about one hour. In H$\alpha$ the period decreases with time and exhibits strong damping. The analysis of 171~Å images shows that the oscillation has two phases, an initial long period phase and a subsequent oscillation with a shorter period. In this wavelength the damping appears weaker than in H$\alpha$. The velocity is the largest ever detected in a prominence oscillation, approximately 100 $\mathrm{km}{\mathrm{s}}^{-1}$. Using SDO/HMI magnetograms we reconstruct the magnetic field of the filaments modeled as flux ropes by using a flux-rope insertion method. Applying seismological techniques we determine that the radii of curvature of the field lines in which cool plasma is condensed are in the range 75-120~Mm, in agreement with the reconstructed field. In addition, we infer a field strength of $\ge 7$ to 30 gauss, depending on the electron density assumed; that is also in agreement with the values from the reconstruction (8-20 gauss). The poloidal flux is zero and the axis flux is of the order of 10${}^{20}$ to 10${}^{21}$ Mx, confirming the high shear existing even in a non-active filament.

Accepted for publication in The Astrophysical Journal

References in corpus (11)

• Multi-scale Gaussian normalization for solar image processing
• Large Amplitude Longitudinal Oscillations in a Solar Filament
• Large amplitude oscillation of a polar crown filament in the pre-eruption phase
• Observations and Implications of Large-Amplitude Longitudinal Oscillations in a Solar Filament
• SOHO/SUMER Observations of Prominence Oscillation Before Eruption
• Large amplitude oscillatory motion along a solar filament
• Magnetic Structure and Dynamics of the Erupting Solar Polar Crown Prominence on 2012 March 12
• Large-Amplitude Oscillation of an Erupting Filament as Seen in EUV, H-alpha and Microwave Observations
• Large-amplitude longitudinal oscillations in a solar filament
• Interaction of two filaments in a long filament channel associated with twin coronal mass ejections
• The effects of magnetic-field geometry on longitudinal oscillations of solar prominences: Cross-sectional area variation for thin tubes