Transverse kink oscillations of inhomogeneous prominence threads: numerical analysis and H$\alpha$ forward modelling

Abstract

Prominence threads are very long and thin flux tubes which are partially filled with cold plasma. Observations have shown that transverse oscillations are frequent in these solar structures. The observations are usually interpreted as the fundamental kink mode, while the detection of the first harmonic remains elusive. Here, we aim to study how the density inhomogeneity in the longitudinal and radial directions modify the periods and damping times of kink oscillations, and how this effect would be reflected in observations. We solve the ideal magnetohydrodynamics equations through two different methods: a) performing 3D numerical simulations, and b) solving a 2D generalised eigenvalue problem. We study the dependence of the periods, damping times and amplitudes of transverse kink oscillations on the ratio between the densities at the centre and at the ends of the tube, and on the average density. We apply forward modelling on our 3D simulations to compute synthetic H$\alpha$ profiles. We confirm that the ratio of the period of the fundamental oscillation mode to the period of the first harmonic increases as the ratio of the central density to the footpoint density is increased or as the averaged density of the tube is decreased. We find that the damping times due to resonant absorption decrease as the central to footpoint density ratio increases. Contrary to the case of longitudinally homogeneous tubes, we find that the damping time to period ratio also increases as the density ratio is increased or the average density is reduced. We present snapshots and time-distance diagrams of the emission in the H$\alpha$ line. The results presented here have implications for the field of prominence seismology. While the H$\alpha$ emission can be used to detect the fundamental mode, the first harmonic is barely detectable in H$\alpha$. This may explain the lack of detections of the first harmonic.

arXiv comment17 pages, 16 figures, 4 movies. Accepted for publication in Astronomy & Astrophysics

References in corpus (31)

• CRISP Spectropolarimetric Imaging of Penumbral Fine Structure
• Nonlinear Instability of kink oscillations due to shear motions
• Magnetohydrodynamic waves in solar partially ionized plasmas: two-fluid approach
• Fine strand-like structure in the solar corona from MHD transverse oscillations
• Resonant Absorption of Transverse Oscillations and Associated Heating in a Solar Prominence. II- Numerical aspects
• Swaying threads of a solar filament
• Collisional dissipation of Alfvén waves in a partially ionised solar chromosphere
• Transverse oscillations of flowing prominence threads observed with Hinode
• Damping of Fast Magnetohydrodynamic Oscillations in Quiescent Filament Threads
• Alfven waves in a partially ionized two-fluid plasma
• Damping of nonlinear standing kink oscillations: a numerical study
• Kelvin-Helmholtz instability in coronal magnetic flux tubes due to azimuthal shear flows
• Modelling observed decay-less oscillations as resonantly enhanced Kelvin-Helmholtz vortices from transverse MHD waves and their seismological application
• Morphology and dynamics of solar prominences from 3D MHD simulations
• Resonantly Damped Kink Magnetohydrodynamic Waves in a Partially Ionized Filament Thread
• Seismology of Standing Kink Oscillations of Solar Prominence Fine Structures
• Numerical simulations of transverse oscillations in radiatively cooling coronal loops
• Two-fluid simulations of waves in the solar chromosphere II. Propagation and damping of fast magneto-acoustic waves and shocks
• Magnetohydrodynamic kink waves in two-dimensional non-uniform prominence threads
• Multi-scale observations of thermal non-equilibrium cycles in coronal loops
• Solar prominences embedded in flux ropes: morphological features and dynamics from 3D MHD simulations
• Non-linear damping of standing kink waves computed with Elsasser variables
• Multi-fluid approach to high-frequency waves in plasmas. III. Nonlinear regime and plasma heating
• Prominence seismology using the period ratio of transverse thread oscillations
• The Effect of Twisted Magnetic Field on the Period Ratio P_1/P_2 of Nonaxisymmetric MHD Waves
• Onset of the Kelvin-Helmholtz instability in partially ionized magnetic flux tubes
• Transition to turbulence in nonuniform coronal loops driven by torsional Alfven waves
• Kink oscillations of flowing threads in solar prominences
• Effects of Stratification and Flows on P1/P2 Ratios and Anti-Node Shifts within Closed Loop Structures
• The effect of flow on resonant absorption of slow MHD waves in magnetic flux tubes
• Inferring physical parameters in solar prominence threads

Cited by in corpus (3)

• 1.5D NLTE spectral synthesis of a 3D filament/prominence simulation
• Radiance Cascades: A Novel High-Resolution Formal Solution for Multidimensional Non-LTE Radiative Transfer
• Transition to turbulence in nonuniform coronal loops driven by torsional Alfvén waves. II. Extended analysis and effect of magnetic twist