CORONAL ALFVÉN SPEED DETERMINATION: CONSISTENCY BETWEEN SEISMOLOGY USING AIA/<i>SDO</i>TRANSVERSE LOOP OSCILLATIONS AND MAGNETIC EXTRAPOLATION

Verwichte, E.; Doorsselaere, Tom Van; Foullon, Claire; White, R. S.

doi:10.1088/0004-637x/767/1/16

Cited by 60 publications

(59 citation statements)

References 50 publications

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“…Modelling this behaviour as a fast magnetoacoustic kink mode allows the observed period of oscillation and loop length to be related to the magnetic field strength and density profile. Verwichte et al (2013) demonstrated that the results of such seismological inversions are consistent with values obtained by magnetic extrapolation and spectral observations. In addition to being a tool for remote plasma diagnostics, MHD waves might also have a significant role in the processes of coronal heating and solar wind acceleration (see e.g.…”

Section: Introductionsupporting

confidence: 87%

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

Pascoe

Goddard

Nisticò

et al. 2016

A&A

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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.

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Section: Introductionsupporting

confidence: 87%

“…Cheung et al 2015), or information about the magnetic field from extrapolations (e.g. Verwichte et al 2013) or numerical simulations (e.g. Chen & Peter 2015), in addition to any improvements to the theoretical modelling of the relevant physical processes.…”

Section: Discussionmentioning

confidence: 99%

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

Pascoe

Goddard

Nisticò

et al. 2016

A&A

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“…The Atmospheric Imaging Assembly (AIA) on board NASA's Solar Dynamics Observatory (SDO) satellite (Lemen et al 2012;Pesnell et al 2012) continues the stream of reported oscillation Appendices are available in electronic form at http://www.aanda.org events and further stimulates interest in these phenomena (e.g. Aschwanden & Schrijver 2011;Wang et al 2012;Gosain 2012;Verwichte et al 2013). Oscillations of this type are normally interpreted as fast kink magnetohydrodynamic (MHD) modes of cylinder-like structures (Edwin & Roberts 1983), and on this basis, procedures have been developed to deduce coronal parameters from wave properties (e.g.…”

Section: Introductionmentioning

confidence: 99%

A unified view of coronal loop contraction and oscillation in flares

Russell

Simões

Fletcher

2015

A&A

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Context. Transverse loop oscillations and loop contractions are commonly associated with solar flares, but the two types of motion have traditionally been regarded as separate phenomena. Aims. We present an observation of coronal loops that contract and oscillate following the onset of a flare. We aim to explain why both behaviours are seen together and why only some of the loops oscillate. Methods. A time sequence of SDO/AIA 171 Å images is analysed to identify the positions of coronal loops following the onset of the M6.4 flare SOL2012-03-09T03:53. We focus on five loops in particular, all of which contract during the flare, with three of them oscillating as well. A simple model is then developed for the contraction and oscillation of a coronal loop. Results. We propose that coronal loop contractions and oscillations can occur in a single response to removal of magnetic energy from the corona. Our model reproduces the various types of loop motion observed and explains why the highest loops oscillate during their contraction, while no oscillation is detected for the shortest contracting loops. The proposed framework suggests that loop motions can be used as a diagnostic for the removal of coronal magnetic energy by flares, while rapid decrease in coronal magnetic energy is a newly identified excitation mechanism for transverse loop oscillations.

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“…For example, standing kink oscillations of coronal loops have been used to infer the coronal magnetic field strength (e.g. Nakariakov et al 1999;Nakariakov & Ofman 2001;White & Verwichte 2012) and it has been demonstrated that seismological inversions are consistent with values obtained by magnetic extrapolation and spectral observations (Verwichte et al 2013a). Magnetohydrodynamic waves might also have a significant role in the processes of coronal heating and solar wind acceleration (e.g.…”

Section: Introductionmentioning

confidence: 95%

Excitation and damping of broadband kink waves in the solar corona

Pascoe

Wright

Moortel

et al. 2015

A&A

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Context. Observations such as those by the Coronal Multi-Channel Polarimeter (CoMP) have revealed that broadband kink oscillations are ubiquitous in the solar corona. Aims. We consider footpoint-driven kink waves propagating in a low β coronal plasma with a cylindrical density structure. We investigate the excitation and damping of propagating kink waves by a broadband driver, including the effects of different spatial profiles for the driver. Methods. We employ a general spatial damping profile in which the initial stage of the damping envelope is approximated by a Gaussian profile and the asymptotic state by an exponential one. We develop a method of accounting for the presence of these different damping regimes and test it using data from numerical simulations. Results. Strongly damped oscillations in low density coronal loops are more accurately described by a Gaussian spatial damping profile than an exponential profile. The consequences for coronal seismology are investigated and applied to observational data for the ubiquitous broadband waves observed by CoMP. Current data cannot distinguish between the exponential and Gaussian profiles because of the levels of noise. We demonstrate the importance of the spatial profile of the driver on the resulting damping profile. Furthermore, we show that a small-scale turbulent driver is inefficient at exciting propagating kink waves.

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CORONAL ALFVÉN SPEED DETERMINATION: CONSISTENCY BETWEEN SEISMOLOGY USING AIA/SDOTRANSVERSE LOOP OSCILLATIONS AND MAGNETIC EXTRAPOLATION

Cited by 60 publications

References 50 publications

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

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

A unified view of coronal loop contraction and oscillation in flares

Excitation and damping of broadband kink waves in the solar corona

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