scholarly journals Weak Damping of Propagating MHD Kink Waves in the Quiescent Corona

2021 ◽  
Vol 923 (2) ◽  
pp. 225
Author(s):  
Richard J. Morton ◽  
Ajay K. Tiwari ◽  
Tom Van Doorsselaere ◽  
James A. McLaughlin
Keyword(s):  
Large Scale ◽  
Density Ratio ◽  
Resonant Absorption ◽  
Coronal Plasma ◽  
Energy Estimates ◽  
Coronal Loops ◽  
Transverse Waves ◽  
Kink Mode ◽  
Kink Waves ◽  
The Waves

Abstract Propagating transverse waves are thought to be a key transporter of Poynting flux throughout the Sun’s atmosphere. Recent studies have shown that these transverse motions, interpreted as the magnetohydrodynamic kink mode, are prevalent throughout the corona. The associated energy estimates suggest the waves carry enough energy to meet the demands of coronal radiative losses in the quiescent Sun. However, it is still unclear how the waves deposit their energy into the coronal plasma. We present the results from a large-scale study of propagating kink waves in the quiescent corona using data from the Coronal Multi-channel Polarimeter (CoMP). The analysis reveals that the kink waves appear to be weakly damped, which would imply low rates of energy transfer from the large-scale transverse motions to smaller scales via either uniturbulence or resonant absorption. This raises questions about how the observed kink modes would deposit their energy into the coronal plasma. Moreover, these observations, combined with the results of Monte Carlo simulations, lead us to infer that the solar corona displays a spectrum of density ratios, with a smaller density ratio (relative to the ambient corona) in quiescent coronal loops and a higher density ratio in active-region coronal loops.

scholarly journals Significance of Cooling Effect on Comprehension of Kink Oscillations of Coronal Loops

2021 ◽  
Vol 7 ◽  
Author(s):  
Daria Shukhobodskaia ◽  
Alexander A. Shukhobodskiy ◽  
Chris J. Nelson ◽  
Michael S. Ruderman ◽  
Robert Erdélyi
Keyword(s):  
Coronal Loop ◽  
Thermal Evolution ◽  
Oscillation Amplitude ◽  
Density Ratio ◽  
Resonant Absorption ◽  
Coronal Loops ◽  
The Past ◽  
Kink Mode ◽  
Mode Oscillation ◽  
Complex Damping

Kink oscillations of coronal loops have been widely studied, both observationally and theoretically, over the past few decades. It has been shown that the majority of observed driven coronal loop oscillations appear to damp with either exponential or Gaussian profiles and a range of mechanisms have been proposed to account for this. However, some driven oscillations seem to evolve in manners which cannot be modeled with purely Gaussian or exponential profiles, with amplification of oscillations even being observed on occasions. Recent research has shown that incorporating the combined effects of coronal loop expansion, resonant absorption, and cooling can cause significant deviations from Gaussian and exponential profiles in damping profiles, potentially explaining increases in oscillation amplitude through time in some cases. In this article, we analyze 10 driven kink oscillations in coronal loops to further investigate the ability of expansion and cooling to explain complex damping profiles. Our results do not rely on fitting a periodicity to the oscillations meaning complexities in both temporal (period changes) and spatial (amplitude changes) can be accounted for in an elegant and simple way. Furthermore, this approach could also allow us to infer some important diagnostic information (such as, for example, the density ratio at the loop foot-points) from the oscillation profile alone, without detailed measurements of the loop and without complex numerical methods. Our results imply the existence of correlations between the density ratio at the loop foot-points and the amplitudes and periods of the oscillations. Finally, we compare our results to previous models, namely purely Gaussian and purely exponential damping profiles, through the calculation of χ2 values, finding the inclusion of cooling can produce better fits in some cases. The current study indicates that thermal evolution should be included in kink-mode oscillation models in the future to help us to better understand oscillations that are not purely Gaussian or exponential.

scholarly journals Transverse waves in coronal flux tubes with thick boundaries: The effect of longitudinal flows

2019 ◽  
Vol 623 ◽  
pp. A32
Author(s):  
Roberto Soler
Keyword(s):  
Singular Term ◽  
Mhd Waves ◽  
Transverse Waves ◽  
Flux Tubes ◽  
Cascade Energy ◽  
Kink Waves ◽  
Frobenius Series ◽  
The Impact ◽  
The Waves ◽  
Boundary Approximation

Observations show that transverse magnetohydrodynamic (MHD) waves and flows are often simultaneously present in magnetic loops of the solar corona. The waves are resonantly damped in the Alfvén continuum because of plasma and/or magnetic field nonuniformity across the loop. The resonant damping is relevant in the context of coronal heating, since it provides a mechanism to cascade energy down to the dissipative scales. It has been theoretically shown that the presence of flow affects the waves propagation and damping, but most of the studies rely on the unjustified assumption that the transverse nonuniformity is confined to a boundary layer much thinner than the radius of the loop. Here we present a semi-analytic technique to explore the effect of flow on resonant MHD waves in coronal flux tubes with thick nonuniform boundaries. We extend a published method, which was originally developed for a static plasma, in order to incorporate the effect of flow. We allowed the flow velocity to continuously vary within the nonuniform boundary from the internal velocity to the external velocity. The analytic part of the method is based on expressing the wave perturbations in the thick nonuniform boundary of the loop as a Frobenius series that contains a singular term accounting for the Alfvén resonance, while the numerical part of the method consists of solving iteratively the transcendental dispersion relation together with the equation for the Alfvén resonance position. As an application of this method, we investigated the impact of flow on the phase velocity and resonant damping length of MHD kink waves. With the present method, we consistently recover results in the thin boundary approximation obtained in previous studies. We have extended those results to the case of thick boundaries. We also explored the error associated with the use of the thin boundary approximation beyond its regime of applicability.

Excitation and damping of disturbances in cylindrical coronal loops

2005 ◽  
Vol 364 (1839) ◽  
pp. 547-550 ◽  
Author(s):  
Jaume Terradas ◽  
Ramón Oliver ◽  
José Luis Ballester
Keyword(s):  
Boundary Layer ◽  
Coronal Loop ◽  
Normal Mode Analysis ◽  
Resonant Absorption ◽  
Time Dependent ◽  
Mode Analysis ◽  
Coronal Loops ◽  
Two Dimensional ◽  
Magnetohydrodynamic Equations ◽  
Kink Mode

The excitation and damping of transversal coronal loop oscillations is studied using one-and two-dimensional models of line-tied cylindrical loops. By solving the time-dependent magnetohydrodynamic equations it is shown how an initial disturbance generated in the solar corona induces kink mode oscillations. We investigate the effect of the disturbance on a loop with a non-uniform boundary layer. In particular, a strong damping of transversal oscillations due to resonant absorption is found, such as predicted by previous works based on normal mode analysis.

Analytical study of plasma heating by resonant absorption of the modified external kink mode

1991 ◽  
Vol 45 (1) ◽  
pp. 3-18 ◽  
Author(s):  
D. Van Eester ◽  
M. Goossens ◽  
S. Poedts
Keyword(s):  
Numerical Simulations ◽  
Large Scale ◽  
Analytical Study ◽  
Plasma Heating ◽  
Resonant Absorption ◽  
Analytic Description ◽  
Hybrid Mode ◽  
Kink Mode ◽  
Basic Physics ◽  
External Kink

A simplified analytic description is used to understand recent results of large-scale numerical simulations of resonant absorption and to disentangle the basic physics. It is shown that very efficient absorption takes place at frequencies where a discrete external kink and an Alfvén continuum mode merge into a modified external kink mode. The relation between this ‘hybrid’ mode and ‘pure’ continuum or discrete spectrum modes is discussed.

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 Wave heating in gravitationally stratified coronal loops in the presence of resistivity and viscosity

2019 ◽  
Vol 623 ◽  
pp. A53 ◽  
Author(s):  
K. Karampelas ◽  
T. Van Doorsselaere ◽  
M. Guo
Keyword(s):  
Energy Dissipation ◽  
Kinetic Energy ◽  
Coronal Loops ◽  
Transverse Waves ◽  
Flux Tubes ◽  
Future Studies ◽  
Mhd Simulations ◽  
Wave Heating ◽  
Kink Waves ◽  
Very High

Context. In recent years, coronal loops have been the focus of studies related to the damping of different magnetohydrodynamic (MHD) surface waves and their connection with coronal seismology and wave heating. For a better understanding of wave heating, we need to take into account the effects of different dissipation coefficients such as resistivity and viscosity, the importance of the loop physical characteristics, and the ways gravity can factor into the evolution of these phenomena. Aims. We aim to map the sites of energy dissipation from transverse waves in coronal loops in the presence and absence of gravitational stratification and to compare ideal, resistive, and viscous MHD. Methods. Using the PLUTO code, we performed 3D MHD simulations of kink waves in single, straight, density-enhanced coronal flux tubes of multiple temperatures. Results. We see the creation of spatially expanded Kelvin–Helmholtz eddies along the loop, which deform the initial monolithic loop profile. For the case of driven oscillations, the Kelvin–Helmholtz instability develops despite physical dissipation, unless very high values of shear viscosity are used. Energy dissipation gets its highest values near the apex, but is present all along the loop. We observe an increased efficiency of wave heating once the kinetic energy saturates at the later stages of the simulation and a turbulent density profile has developed. Conclusions. The inclusion of gravity greatly alters the dynamic evolution of our systems and should not be ignored in future studies. Stronger physical dissipation leads to stronger wave heating in our set-ups. Finally, once the kinetic energy of the oscillating loop starts saturating, all the excess input energy turns into internal energy, resulting in more efficient wave heating.

scholarly journals Transverse motions in sunspot super-penumbral fibrils

2020 ◽  
Vol 379 (2190) ◽  
pp. 20200183 ◽  
Author(s):  
R. J. Morton ◽  
K. Mooroogen ◽  
V. M. J. Henriques
Keyword(s):  
High Resolution ◽  
Transverse Wave ◽  
Wave Energy ◽  
Solar Telescope ◽  
Transverse Waves ◽  
Wave Dynamics ◽  
Kink Mode ◽  
The Waves ◽  
Wave Phenomena ◽  
Lower Solar Atmosphere

Sunspots have played a key role in aiding our understanding of magnetohydrodynamic (MHD) wave phenomena in the Sun’s atmosphere, and it is well known they demonstrate a number of wave phenomena associated with slow MHD modes. Recent studies have shown that transverse wave modes are present throughout the majority of the chromosphere. Using high-resolution Ca II 8542 Å observations from the Swedish Solar Telescope, we provide the first demonstration that the chromospheric super-penumbral fibrils, which span out from the sunspot, also show ubiquitous transverse motions. We interpret these motions as transverse waves, in particular the MHD kink mode. We compile the statistical properties of over 2000 transverse motions to find distributions for periods and amplitudes, finding they are broadly consistent with previous observations of chromospheric transverse waves in quiet Sun fibrils. The very presence of the waves in super-penumbral fibrils raises important questions about how they are generated, and could have implications for our understanding of how MHD wave energy is transferred through the atmosphere of a sunspot. This article is part of the Theo Murphy meeting issue ‘High-resolution wave dynamics in the lower solar atmosphere’.

scholarly journals Coupled Alfvén and kink oscillations in an inhomogeneous corona

2010 ◽  
Vol 6 (S274) ◽  
pp. 129-132
Author(s):  
David J. Pascoe ◽  
Andrew N. Wright ◽  
Ineke De Moortel
Keyword(s):  
Solar Corona ◽  
Numerical Simulations ◽  
Density Profile ◽  
Transverse Velocity ◽  
Resonant Absorption ◽  
Velocity Perturbation ◽  
Transverse Waves ◽  
Kink Mode ◽  
Kink Wave ◽  
Good Agreement

AbstractWe perform 3D numerical simulations of footpoint-driven transverse waves propagating in a low β plasma. The presence of inhomogeneities in the density profile leads to the coupling of the driven kink mode to Alfvén modes by resonant absorption. The decay of the propagating kink wave as energy is transferred to the local Alfvén mode is in good agreement with a modified interpretation of the analytical expression derived for standing kink modes. This coupling may account for the damping of transverse velocity perturbation waves which have recently been observed to be ubiquitous in the solar corona.

scholarly journals Resonant absorption of kink oscillations in coronal flux tubes with continuous magnetic twist

2019 ◽  
Vol 490 (2) ◽  
pp. 1644-1651 ◽  
Author(s):  
Zanyar Ebrahimi ◽  
Karam Bahari
Keyword(s):  
Magnetic Field ◽  
Resonant Absorption ◽  
Realistic Model ◽  
Mhd Equations ◽  
Flux Tubes ◽  
Kink Mode ◽  
Background Magnetic Field ◽  
Inhomogeneous Density ◽  
Kink Wave ◽  
Kink Waves

ABSTRACT There are observational evidences for the existence of twisted magnetic field in the solar corona. Here, we have investigated resonant damping of the magnetohydrodynamic (MHD) kink waves in magnetic flux tubes. A realistic model of the tube with continuous magnetic twist and radially inhomogeneous density profile has been considered. We have obtained the dispersion relation of the kink wave using the solution to the linear MHD equations outside the density inhomogeneity and the appropriate connection formula to the solutions across the thin transitional boundary layer. The dependence of the oscillation frequency and damping rate of the waves on the twist parameter and longitudinal wavenumber has been investigated. For the flux tube parameters considered in this paper, we obtain rapid damping of the kink waves comparable to the observations. In order to justify this rapid damping, depending on the sign of the azimuthal kink mode number, $m=+1$ or $-1$, the background magnetic field must have left- or right-handed twisted profile, respectively. For the model considered here, the resonant absorption occurs only when the twist parameter is in a range specified by the density contrast.

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.

Sign in / Sign up

Export Citation Format

Share Document