Coupled Alfvén and Kink Oscillations in Coronal Loops

Pascoe, D. J.; Wright, Andrew N.; Moortel, I. De

doi:10.1088/0004-637x/711/2/990

Cited by 118 publications

(178 citation statements)

References 34 publications

(56 reference statements)

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“…Hence the oscillation amplitude is described by a kind of Gaussian profile for small time and by the exponential function for larger time. This result is similar to one found by Pascoe et al (2010Pascoe et al ( , 2011Pascoe et al ( , 2012 for propagating waves. The dashed line in (30) we obtain t dc /Π = 4(π 2 κ) −1 .…”

Section: Examination Of Figs 1-3 Reveals That the Solution Can Be Wrsupporting

confidence: 91%

“…In particular, it was shown with the use of connection formulae that in the linear approximation the waves damp exponentially with the distance from the driver, and the damping length has been calculated. The same problem has been studied numerically by Pascoe et al (2010Pascoe et al ( , 2011Pascoe et al ( , 2012. In particular, Pascoe et al (2012) have shown that the wave amplitude does not decay exponentially everywhere.…”

Section: Introductionmentioning

confidence: 95%

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Damping of coronal loop kink oscillations due to mode conversion

Рудерман

Terradas

2013

A&A

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The damping of kink oscillations of a thin magnetic tube due to mode conversion, also called resonant absorption, is studied. The tube consists of a homogeneous core region and an inhomogeneous annulus, where the density monotonically decreases from its value in the core region to the value in the surrounding plasma. The annulus is assumed to be thin, so the study is carried out in the thin tube thin boundary approximation. The equation governing the amplitude variation of kink oscillations is derived. The initial value problem for this equation is solved to study the resonant damping. This means that, in particular, we study the transient state before the loop oscillates with the stationary or nearly stationary state. The results are compared with those of the direct numerical modelling, and the agreement is found to be fairly good. On the basis of the solution to the initial value problem for the governing equation, the damping time is calculated and compared with that given by the classical theory of resonant absorption. It is found that the classical theory underestimates the damping time, with the error increasing with the increase of the annulus thickness. However, the error is not large, so the damping time given by the classical theory of resonant absorption can be taken as a sufficiently good approximation.

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Section: Examination Of Figs 1-3 Reveals That the Solution Can Be Wrsupporting

confidence: 91%

Section: Introductionmentioning

confidence: 95%

Damping of coronal loop kink oscillations due to mode conversion

Рудерман

Terradas

2013

A&A

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“…These azimuthal motions keep propagating along magnetic field lines (see the numerical simulations by, e.g., Pascoe et al 2010Pascoe et al , 2011. A detailed investigation of the energy transfer in the case of standing waves was done in Arregui et al (2011) by analyzing the Poynting flux in a two-dimensional configuration.…”

Section: Chromospheric Kink Wavesmentioning

confidence: 99%

“…In magnetic waveguides resonant absorption transfers wave energy from transverse kink motions to azimuthal motions localized in the inhomogeneous part of the waveguide. This process has been studied numerically by Pascoe et al (2010Pascoe et al ( , 2011 in the case of driven kink waves in coronal waveguides.…”

Section: Introductionmentioning

confidence: 99%

Resonant Alfvén waves in partially ionized plasmas of the solar atmosphere

Soler

Andries

Goossens

2012

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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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“…They are strongly damped in loop structures (Tomczyk & McIntosh 2009) which is also accounted for by mode coupling (e.g. Pascoe et al 2010;Terradas et al 2010). The propagating kink waves are observed to have a broadband power spectrum.…”

Section: Discussionmentioning

confidence: 99%

Spatially resolved observation of the fundamental and second harmonic standing kink modes using SDO/AIA

Pascoe

Goddard

Nakariakov

2016

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Aims. We consider a coronal loop kink oscillation observed by the Atmospheric Imaging Assembly (AIA) of the Solar Dynamics Observatory (SDO) which demonstrates two strong spectral components. The period of the lower frequency component being approximately twice that of the shorter frequency component suggests the presence of harmonics. Methods. We examine the presence of two longitudinal harmonics by investigating the spatial dependence of the loop oscillation. The time-dependent displacement of the loop is measured at 15 locations along the loop axis. For each position the detrended displacement is fitted as the sum of two damped sinusoids, having periods P 1 and P 2 , and a damping time τ. The shorter period component exhibits anti-phase oscillations in the loop legs. Results. We interpret the observation in terms of the first (global or fundamental) and second longitudinal harmonics of the standing kink mode. The strong excitation of the second harmonic appears connected to the preceding coronal mass ejection (CME) which displaced one of the loop legs. The oscillation parameters found are P 1 " 5.00˘0.62 minutes, P 2 " 2.20˘0.23 minutes, P 1 {2P 2 " 1.15˘0.22, and τ{P " 3.35˘1.45.

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Coupled Alfvén and Kink Oscillations in Coronal Loops

Cited by 118 publications

References 34 publications

Damping of coronal loop kink oscillations due to mode conversion

Damping of coronal loop kink oscillations due to mode conversion

Resonant Alfvén waves in partially ionized plasmas of the solar atmosphere

Spatially resolved observation of the fundamental and second harmonic standing kink modes using SDO/AIA

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