Swaying Threads of a Solar Filament

Lin, Yong; Soler, Roberto; Engvold, O.; Ballester, J. L.; Langangen, Øystein; Oliver, R.; Voort, L. H. M. Rouppe van der

doi:10.1088/0004-637x/704/1/870

Cited by 121 publications

(201 citation statements)

References 32 publications

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“…Recent observations of Alfvénic transverse waves in spicules have been reported by, e.g, De Pontieu et al (2007), Zaqarashvili et al (2007), Kim et al (2008), He et al (2009a,b), Okamoto & De Pontieu (2011). In addition, propagating transverse waves in thin threads of solar prominences have been observed (e.g., Lin et al 2007Lin et al , 2009) and Alfvénic waves in bright points have been reported (Jess et al 2009). The role and implications of the observed Alfvénic waves for the heating of the solar atmosphere have been discussed by, e.g., Erdélyi & Fedun (2007); De Pontieu et al (2007); McIntosh et al (2011);Cargill & De Moortel (2011).…”

Section: Introductionmentioning

confidence: 91%

Resonant Alfvén waves in partially ionized plasmas of the solar atmosphere

Soler

Andries

Goossens

2012

A&A

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Context. Magnetohydrodynamic (MHD) waves are ubiquitous in the solar atmosphere. In magnetic waveguides resonant absorption due to plasma inhomogeneity naturally transfers wave energy from large-scale motions to small-scale motions. In the cooler parts of the solar atmosphere as, e.g., the chromosphere, effects due to partial ionization may be relevant for wave dynamics and heating. Aims. We study resonant Alfvén waves in partially ionized plasmas. Methods. We use the multifluid equations in the cold plasma approximation. We investigate propagating resonant MHD waves in partially ionized flux tubes. We use approximate analytical theory based on normal modes in the thin tube and thin boundary approximations along with numerical eigenvalue computations. Results. We find that the jumps of the wave perturbations across the resonant layer are the same as in fully ionized plasmas. The damping length due to resonant absorption is inversely proportional to the frequency, while that due to ion-neutral collisions is inversely proportional to the square of the frequency. For observed frequencies in the solar atmosphere, the amplitude of MHD kink waves is more efficiently damped by resonant absorption than by ion-neutral collisions. Conclusions. Most of the energy carried by chromospheric kink waves is converted into localized azimuthal Alfvén waves that can deposit energy in the coronal medium. The dissipation of wave energy in the chromosphere due to ion-neutral collisions is only effective for high-frequency waves. The chromosphere acts as a filter for kink waves with periods shorter than 10 s.

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Section: Introductionmentioning

confidence: 91%

Resonant Alfvén waves in partially ionized plasmas of the solar atmosphere

Soler

Andries

Goossens

2012

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“…We have used the averaged values of loop radius and length. However, for kink waves in filament threads (Lin et al 2009) or torsional Alfvén waves in chromospheric magnetic bright points (Jess et al 2009) many have values of k z R ≈ 1. It is relatively straightforward to relax the TT approximation and to consider the effect of the finite tube radius on damping.…”

Section: Spatial Damping Beyond the Tt Approximationmentioning

confidence: 99%

Selective spatial damping of propagating kink waves due to resonant absorption

Terradas

Goossens

Verth

2010

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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.

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“…To do so, we set the wavenumber component in the perpendicular direction to magnetic field lines to a fixed value, k z L = π/2, with L a typical length-scale in the perpendicular direction. Since highresolution observations of filaments (see, e.g., Lin et al 2007Lin et al , 2009 show fine structures (threads) with a typical width of ∼100 km, we select L = 10 5 m as our perpendicular lengthscale. Therefore, the propagation angle θ now depends on k x , We see that the behavior of the three solutions is substantially different from that of the free propagation case.…”

Section: Constrained Propagation By a Waveguidementioning

confidence: 99%

Time damping of non-adiabatic magnetohydrodynamic waves in a partially ionized prominence plasma: effect of helium

Soler

Oliver

Ballester

2010

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Context. Prominences are partially ionized, magnetized plasmas embedded in the solar corona. Damped oscillations and propagating waves are commonly observed. These oscillations have been interpreted in terms of magnetohydrodynamic (MHD) waves. Ion-neutral collisions and non-adiabatic effects (radiation losses and thermal conduction) have been proposed as damping mechanisms. Aims. We study the effect of the presence of helium on the time damping of non-adiabatic MHD waves in a plasma composed by electrons, protons, neutral hydrogen, neutral helium (He i), and singly ionized helium (He ii) in the single-fluid approximation.Methods. The dispersion relation of linear non-adiabatic MHD waves in a homogeneous, unbounded, and partially ionized prominence medium is derived. We compute the period and the damping time of Alfvén, slow, fast, and thermal waves. A parametric study of the ratio of the damping time to the period with respect to the helium abundance is performed.Results. The efficiency of ion-neutral collisions, as well as thermal conduction, is increased by the presence of helium. However, if realistic abundances of helium in prominences (∼10%) are considered, this has a minor influence on the wave damping. Conclusions. The presence of helium can be safely neglected in studies of MHD waves in partially ionized prominence plasmas.

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Swaying Threads of a Solar Filament

Cited by 121 publications

References 32 publications

Resonant Alfvén waves in partially ionized plasmas of the solar atmosphere

Resonant Alfvén waves in partially ionized plasmas of the solar atmosphere

Selective spatial damping of propagating kink waves due to resonant absorption

Time damping of non-adiabatic magnetohydrodynamic waves in a partially ionized prominence plasma: effect of helium

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