scholarly journals The damping of transverse oscillations of prominence threads: a comparative study

2013 ◽  
Vol 8 (S300) ◽  
pp. 48-51 ◽  
Author(s):  
Roberto Soler ◽  
Ramon Oliver ◽  
Jose Luis Ballester
Keyword(s):  
Comparative Study ◽  
Thermal Conduction ◽  
Resonant Absorption ◽  
Radiative Cooling ◽  
Magnetohydrodynamic Waves ◽  
Physical Mechanisms ◽  
Solar Prominences ◽  
Kink Waves ◽  
Conduction Cooling ◽  
Transverse Oscillations

AbstractTransverse oscillations of thin threads in solar prominences are frequently reported in high-resolution observations. The typical periods of the oscillations are in the range of 3 to 20 min. A peculiar feature of the oscillations is that they are damped in time, with short damping times corresponding to few periods. Theoretically, the oscillations are interpreted as kink magnetohydrodynamic waves. However, the mechanism responsible for the damping is not well known. Here we perform a comparative study between different physical mechanisms that may damp kink waves in prominence threads. The considered processes are thermal conduction, cooling by radiation, resonant absorption, and ion-neutral collisions. We find that thermal conduction and radiative cooling are very inefficient for the damping of kink waves. The effect of ion-neutral collisions is minor for waves with periods usually observed. Resonant absorption is the only process that produces an efficient damping. The damping times theoretically predicted by resonant absorption are compatible with those reported in the observations.

scholarly journals 3D numerical simulations of oscillations in solar prominences

2020 ◽  
Vol 633 ◽  
pp. A113 ◽  
Author(s):  
A. Adrover-González ◽  
J. Terradas
Keyword(s):  
Numerical Simulations ◽  
Resonant Absorption ◽  
Oscillation Period ◽  
Restoring Force ◽  
Solar Prominences ◽  
Pendulum Model ◽  
Wide Range ◽  
Ideal Magnetohydrodynamic ◽  
High Order Finite Difference ◽  
Transverse Oscillations

Context. Oscillations in solar prominences are a frequent phenomenon, and they have been the subject of many studies. A full understanding of the mechanisms that drive them and their attenuation has not been reached yet, however. Aims. We numerically investigate the periodicity and damping of transverse and longitudinal oscillations in a 3D model of a curtain-shaped prominence. Methods. We carried out a set of numerical simulations of vertical, transverse and longitudinal oscillations with the high-order finite-difference Pencil Code. We solved the ideal magnetohydrodynamic equations for a wide range of parameters, including the width (wx) and density (ρp0) of the prominence, and the magnetic field strength (B) of the solar corona. We studied the periodicity and attenuation of the induced oscillations. Results. We found that longitudinal oscillations can be fit with the pendulum model, whose restoring force is the field-aligned component of gravity, but other mechanisms such as pressure gradients may contribute to the movement. On the other hand, transverse oscillations are subject to magnetic forces. The analysis of the parametric survey shows, in agreement with observational studies, that the oscillation period (P) increases with the prominence width. For transverse oscillations we obtained that P increases with density and decreases with B. For longitudinal oscillations we also found that P increases with ρp0, but there are no variations with B. The attenuation of transverse oscillations was investigated by analysing the velocity distribution and computing the Alfvén continuum modes. We conclude that resonant absorption is the mean cause. Damping of longitudinal oscillations is due to some kind of shear numerical viscosity. Conclusions. Our model is a good approximation of a prominence body that nearly reproduces the observed oscillations. However, more realistic simulations that include other terms such as non-adiabatic processes or partially ionised plasmas are necessary to obtain better results.

Damping of magnetohydrodynamic waves by resonant absorption in the solar atmosphere

2005 ◽  
Vol 364 (1839) ◽  
pp. 433-446 ◽  
Author(s):  
M Goossens ◽  
J Andries ◽  
I Arregui
Keyword(s):  
Resonant Absorption ◽  
Mhd Waves ◽  
Coronal Loops ◽  
Two Dimensional ◽  
Heliospheric Observatory ◽  
Magnetohydrodynamic Waves ◽  
One Dimensional ◽  
Magnetic Structures ◽  
Different Types ◽  
Kink Waves

In the last decade we have been overwhelmed by an avalanche of discoveries of magnetohydrodynamic (MHD) waves by the Solar and Heliospheric Observatory and Transition Region and Coronal Explorer observatories. Both standing and propagating versions of fast magnetoacoustic and slow magnetoacoustic MHD waves have been detected. Information on the damping times and damping distances of these waves is less detailed and less accurate than that on periods and amplitudes. Nevertheless, observations show the damping times and damping lengths are often short. Also, different types of MHD waves in different types of magnetic structures likely require different damping mechanisms. The phenomenon of fast damping is well documented for the standing fast magnetosonic kink waves in coronal loops. This paper concentrates on standing fast magnetosonic waves. It reports on results on periods and damping times due to resonant absorption in one-dimensional and two-dimensional models of coronal loops. Special attention is given to multiple modes.

scholarly journals Seismology of kink oscillations in coronal loops: Two decades of resonant damping

2007 ◽  
Vol 3 (S247) ◽  
pp. 228-242 ◽  
Author(s):  
Marcel Goossens
Keyword(s):  
Wave Theory ◽  
Resonant Absorption ◽  
Mhd Waves ◽  
Coronal Loops ◽  
Equilibrium Models ◽  
Kink Waves ◽  
The Common ◽  
Uniform Equilibrium ◽  
Transverse Oscillations ◽  
Alfven Velocity

AbstractThe detection of rapidly damped transverse oscillations in coronal loops by Aschwanden et al. (1999) and Nakariakov et al. (1999) gave a strong impetus to the study of MHD waves and their damping. The common interpretation of the observations of these oscillations is based on kink modes. This paper reviews how the observed period and damping time can be reproduced by MHD wave theory when non-uniform equilibrium models are considered that have a transversal variation of the local Alfven velocity. The key point here is that resonant absorption cannot be avoided and occurs as natural damping mechanism for kink waves in non-uniform equilibrium models. The present paper starts with work by Hollweg & Yang (1988) and discusses subsequent developments in theory and their applications to seismology of coronal loops. It addresses the consistent use of observations of periods and damping times as seismological tools within the framework of resonant absorption. It shows that within the framework of resonant absorption infinitely many equilibrium models can reproduce the observed values of periods and damping times.

Linear Visco-Resistive Computations of Magnetohydrodynamic Waves: I. The Code and Test Cases

1994 ◽  
Vol 144 ◽  
pp. 503-505
Author(s):  
R. Erdélyi ◽  
M. Goossens ◽  
S. Poedts
Keyword(s):  
Resonant Absorption ◽  
Numerical Code ◽  
Mhd Waves ◽  
Test Cases ◽  
Numerical Accuracy ◽  
Element Discretization ◽  
Flux Tubes ◽  
Magnetohydrodynamic Waves ◽  
Viscosity Coefficients ◽  
Magnetic Flux Tubes

AbstractThe stationary state of resonant absorption of linear, MHD waves in cylindrical magnetic flux tubes is studied in viscous, compressible MHD with a numerical code using finite element discretization. The full viscosity tensor with the five viscosity coefficients as given by Braginskii is included in the analysis. Our computations reproduce the absorption rates obtained by Lou in scalar viscous MHD and Goossens and Poedts in resistive MHD, which guarantee the numerical accuracy of the tensorial viscous MHD code.

scholarly journals Excitation of decay-less transverse oscillations of coronal loops by random motions

2020 ◽  
Vol 633 ◽  
pp. L8 ◽  
Author(s):  
A. N. Afanasyev ◽  
T. Van Doorsselaere ◽  
V. M. Nakariakov
Keyword(s):  
Broad Band ◽  
Random Excitation ◽  
Forced Oscillations ◽  
Oscillatory Process ◽  
Coronal Loops ◽  
Alternative Mechanism ◽  
Steady Flows ◽  
Kink Waves ◽  
Random Motions ◽  
Transverse Oscillations

Context. The relatively large-amplitude decaying regime of transverse oscillations of coronal loops has been known for two decades and has been interpreted in terms of magnetohydrodynamic kink modes of cylindrical plasma waveguides. In this regime oscillations decay in several cycles. Recent observational analysis has revealed so-called decay-less, small-amplitude oscillations, in which a multi-harmonic structure has been detected. Several models have been proposed to explain these oscillations. In particular, decay-less oscillations have been described in terms of standing kink waves driven with continuous mono-periodic motions of loop footpoints, in terms of a simple oscillator model of forced oscillations due to harmonic external force, and as a self-oscillatory process due to the interaction of a loop with quasi-steady flows. However, an alternative mechanism is needed to explain the simultaneous excitation of several longitudinal harmonics of the oscillation. Aims. We study the mechanism of random excitation of decay-less transverse oscillations of coronal loops. Methods. With a spatially one-dimensional and time-dependent analytical model taking into account effects of the wave damping and kink speed variation along the loop, we considered transverse loop oscillations driven by random motions of footpoints. The footpoint motions were modelled by broad-band coloured noise. Results. We found the excitation of loop eigenmodes and analysed their frequency ratios as well as the spatial structure of the oscillations along the loop. The obtained results successfully reproduce the observed properties of decay-less oscillations. In particular, excitation of eigenmodes of a loop as a resonator can explain the observed quasi-monochromatic nature of decay-less oscillations and the generation of multiple harmonics detected recently. Conclusions. We propose a mechanism that can interpret decay-less transverse oscillations of coronal loops in terms of kink waves randomly driven at the loop footpoints.

scholarly journals Thermal flux limitation and thermal conduction inhibition in laser plasma

1985 ◽  
Vol 3 (3) ◽  
pp. 243-250 ◽  
Author(s):  
Tan Weihan ◽  
Gu Min
Keyword(s):  
Distribution Function ◽  
Numerical Calculation ◽  
Laser Plasma ◽  
Thermal Conduction ◽  
Electron Distribution ◽  
Electron Distribution Function ◽  
Thermal Flux ◽  
Physical Mechanisms ◽  
Laser Plasmas ◽  
Flux Limitation

The physical mechanisms of thermal flux limitation and thermal conduction inhibition in laser plasmas are analyzed. A numerical calculation accounting for the non-negative electron distribution function and pressure gradient has been given.

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