Resonantly damped fast MHD kink modes in longitudinally stratified tubes with thick non-uniform transitional layers

Arregui, I.; Doorsselaere, Tom Van; Andries, Jesse; Goossens, Marcel; Kimpe, Dries

doi:10.1051/0004-6361:20053039

Cited by 64 publications

(78 citation statements)

References 30 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…This damping time has been tested numerically by Steinolfson & Davila (1993). In addition, Poedts & Kerner (1991) and Arregui et al (2005) found that the damping rate is independent of the magnetic diffusivity (although this is only true for resonant absorption). Comparing the two systems (i.e., Figs.…”

Section: Discussionmentioning

confidence: 99%

Three‐dimensional Magnetohydrodynamic Wave Behavior in Active Regions: Individual Loop Density Structure

McLaughlin

Ofman

2008

ApJ

View full text Add to dashboard Cite

We present the numerical results from a three-dimensional (3D) nonlinear MHD simulation of wave activity in an idealized active region in which individual, realistic loop density structure is included. The active region is modeled by an initially force-free, dipole magnetic configuration with gravitationally stratified density and contains a loop with a higher density than its surroundings. This study represents an extension to the model of Ofman & Thompson. As found in their work, we see that fast wave propagation is distorted by the Alfvén speed profile and that the wave propagation generates field line oscillations, which are rapidly damped. We find that the addition of a high-density loop significantly changes the behavior inside that loop, specifically in that the loop can support trapped waves. We also find that the impact of the fast wave impulsively excites both horizontal and vertical loop oscillations. From a parametric study of the oscillations, we find that the amplitude of the oscillations decreases with increasing density contrast, whereas the period and damping time increase. This is one of the key results presented here: that individual loop density structure can influence the damping rate, and specifically that the damping time increases with increasing density contrast. All these results were compared with an additional study performed on a straight coronal loop with similar parameters. Through comparison with the straight loop, we find that the damping mechanism in our curved loop is wave leakage due to curvature. The work performed here highlights the importance of including individual loop density structure in the modeling of active regions and illustrates the need for obtaining accurate density measurements for coronal seismology.

show abstract

Section: Discussionmentioning

confidence: 99%

Three‐dimensional Magnetohydrodynamic Wave Behavior in Active Regions: Individual Loop Density Structure

McLaughlin

Ofman

2008

ApJ

View full text Add to dashboard Cite

show abstract

“…Pascoe et al 2007a), although it is beyond the scope of the present paper. Calculations by Van Doorsselaere et al (2004) and Arregui et al (2005) suggest that the effect of the finite inhomogeneous layer on the period of oscillation can be important for 1, and so might be relevant for our loops 1 and 2. Yu et al (2015) also show that the choice of density profile in the inhomogeneous layer has a small effect on the period of oscillation for standing kink modes in magnetic slabs.…”

Section: Dispersion Diagramsmentioning

confidence: 91%

Coronal loop seismology using damping of standing kink oscillations by mode coupling

Pascoe

Goddard

Nisticò

et al. 2016

A&A

View full text Add to dashboard Cite

Context. Kink oscillations of solar coronal loops are frequently observed to be strongly damped. The damping can be explained by mode coupling on the condition that loops have a finite inhomogeneous layer between the higher density core and lower density background. The damping rate depends on the loop density contrast ratio and inhomogeneous layer width. Aims. The theoretical description for mode coupling of kink waves has been extended to include the initial Gaussian damping regime in addition to the exponential asymptotic state. Observation of these damping regimes would provide information about the structuring of the coronal loop and so provide a seismological tool. Methods. We consider three examples of standing kink oscillations observed by the Atmospheric Imaging Assembly (AIA) of the Solar Dynamics Observatory (SDO) for which the general damping profile (Gaussian and exponential regimes) can be fitted. Determining the Gaussian and exponential damping times allows us to perform seismological inversions for the loop density contrast ratio and the inhomogeneous layer width normalised to the loop radius. The layer width and loop minor radius are found separately by comparing the observed loop intensity profile with forward modelling based on our seismological results. Results. The seismological method which allows the density contrast ratio and inhomogeneous layer width to be simultaneously determined from the kink mode damping profile has been applied to observational data for the first time. This allows the internal and external Alfvén speeds to be calculated, and estimates for the magnetic field strength can be dramatically improved using the given plasma density. Conclusions. The kink mode damping rate can be used as a powerful diagnostic tool to determine the coronal loop density profile. This information can be used for further calculations such as the magnetic field strength or phase mixing rate.

show abstract

“…To model this loop multi-thread structure, Terradas et al (2008) has numerically solved the initial value problem and found that the process of resonant absorption was still an efficient damping mechanism in more complex and realistically structured loop models (see also the work of Ofman 2005). Further study into the properties of standing kink waves has also been undertaken relating plasma inhomogeneity in the direction of the magnetic field caused by, e.g., density (Díaz et al 2004;Andries et al 2005b;Arregui et al 2005;Dymova & Ruderman 2006;Verth et al 2007) or magnetic Ruderman et al 2008) stratification. It was shown that eigenfrequencies and eigenfunctions of coronal loops with longitudinal stratification were altered in such a way that one could determine, e.g., the coronal density scale height by estimating the ratio of the fundamental mode to that of higher overtones, a technique first proposed by Andries et al (2005a) and later developed by to correct for magnetic stratification.…”

Section: Introductionmentioning

confidence: 99%

Selective spatial damping of propagating kink waves due to resonant absorption

Terradas

Goossens

Verth

2010

A&A

Self Cite

126

143

View full text Add to dashboard Cite

Context. There is observational evidence of propagating kink waves driven by photospheric motions. These disturbances, interpreted as kink magnetohydrodynamic (MHD) waves are attenuated as they propagate upwards in the solar corona. Aims. We show that resonant absorption provides a simple explanation to the spatial damping of these waves. Methods. Kink MHD waves are studied using a cylindrical model of solar magnetic flux tubes, which includes a non-uniform layer at the tube boundary. Assuming that the frequency is real and the longitudinal wavenumber complex, the damping length and damping per wavelength produced by resonant absorption are analytically calculated in the thin tube (TT) approximation, valid for coronal waves. This assumption is relaxed in the case of chromospheric tube waves and filament thread waves. Results. The damping length of propagating kink waves due to resonant absorption is a monotonically decreasing function of frequency. For kink waves with low frequencies, the damping length is exactly inversely proportional to frequency, and we denote this as the TGV relation. When moving to high frequencies, the TGV relation continues to be an exceptionally good approximation of the actual dependency of the damping length on frequency. This dependency means that resonant absorption is selective as it favours lowfrequency waves and can efficiently remove high-frequency waves from a broad band spectrum of kink waves. The efficiency of the damping due to resonant absorption depends on the properties of the equilibrium model, in particular on the width of the non-uniform layer and the steepness of the variation in the local Alfvén speed. Conclusions. Resonant absorption is an effective mechanism for the spatial damping of propagating kink waves. It is selective because the damping length is inversely proportional to frequency so that the damping becomes more severe with increasing frequency. This means that radial inhomogeneity can cause solar waveguides to be a natural low-pass filter for broadband disturbances. Kink wave trains travelling along, e.g., coronal loops, will therefore have a greater proportion of the high-frequency components dissipated lower down in the atmosphere. This could have important consequences for the spatial distribution of wave heating in the solar atmosphere.

show abstract

Resonantly damped fast MHD kink modes in longitudinally stratified tubes with thick non-uniform transitional layers

Cited by 64 publications

References 30 publications

Three‐dimensional Magnetohydrodynamic Wave Behavior in Active Regions: Individual Loop Density Structure

Three‐dimensional Magnetohydrodynamic Wave Behavior in Active Regions: Individual Loop Density Structure

Coronal loop seismology using damping of standing kink oscillations by mode coupling

Selective spatial damping of propagating kink waves due to resonant absorption

Contact Info

Product

Resources

About