The 10th december of 2021 Valeriia Kiakh presented his PhD thesis: Large-Amplitude Oscillation in Erupting and Quiescent Solar Prominences
Title: Large-Amplitude Oscillation in Erupting and Quiescent Solar Prominences
Author: Valeriia Kiakh
Directors:Dr. Manuel Luna and Dra. Elena Khomenko
Date: 21 december 2021
Abstract:
In this thesis, we focus on studying the properties of the large-amplitude prominence oscillations (LAOs) using the realistic prominence models and the triggering of such motions by external perturbations. LAOs involve motions with velocity amplitudes above 20 km/s, and large portions of the filament move in phase, indicating a strong connection with the magnetic field structure of the filament. Such motions are triggered by solar energetic events such as distant or nearby flares, jets, and eruptions. The motivation of this work comes from the recent studies showing that LAOs are very common in prominences and open a new window to study the prominence structure by means of a technique known as prominence seismology, which combines observations and theoretical modeling of LAOs. This study is based on time-dependent numerical simulations performed with the magnetohydrodynamic (MHD) code MANCHA3D.
First, we have performed 2.5D numerical simulations of LAOs using a magnetic flux rope model formed from a sheared arcade configuration using converging motions at the foot points and artificially loading
the prominence mass in the magnetic dips of the flux rope. We then apply horizontal and vertical perturbations to excite the different oscillation modes. We have also studied the excitation of the LAOs in the flux rope prominence by an external perturbation. This experiment shows that the wave from the energetic event strongly perturbs the flux rope magnetic field structure. The external disturbance perturbs the flux rope, exciting oscillations of both polarizations. Their properties are a mixture of those excited by purely horizontal and vertical excitation.
Second, we have studied the influence of spatial resolution on numerical experiments of LALOs. We have performed time-dependent numerical simulations of LALOs using the 2D magnetic configuration with the prominence mass loaded at its dips. The triggering of LALOs has been done by perturbing the prominence mass along the magnetic field. The experiments with four values of spatial resolution, 240, 120, 60, and
30 km, have been considered. Our study reveals that highresolution experiments are crucial when investigating the periods and the damping mechanism of LALOs. The period agrees well with the pendulum model only when using a sufficiently high spatial resolution. The results suggest that numerical diffusion in simulations with insufficient spatial resolution can hide important physical effects, such as the
amplification of the oscillations.
Third, we have investigated LAOs in flux rope prominence triggered by self-consistent perturbation associated with an eruptive event near the flux rope prominence. The analysis of the oscillatory motions of the prominence plasma in the flux rope shows that only small-amplitude oscillations (SAOs) are excited due to the nearby eruption and the plasmoid instability. The motions have a complex character showing a mixture of longitudinal and transverse oscillations with short and long periods.
22.
The simulation results suggest that LAOs are complex manifestations of the prominence dynamics involving various excitation and attenuation mechanisms. In this thesis, we have extended the knowledge of the nature of LAOs and advanced the current modeling of these structures by performing multidimensional numerical simulations.
