Determination of the cross-field density structuring in coronal waveguides using the damping of transverse waves

Arregui, I.; Ramos, A. Asensio

doi:10.1051/0004-6361/201423536

Cited by 20 publications

(21 citation statements)

References 29 publications

(39 reference statements)

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“…This curve is based on the general damping profile Eq. (1) and is qualitatively the same as that for the exponential damping regime (dashed curve) alone which has been discussed by previous authors (e.g., Goossens et al 2008;Arregui & Asensio Ramos 2014). A seismological inversion for the density profile parameters (ρ 0 {ρ e , ϵ) based only on the overall damping rate produces a 1D curve in the 2D parameter space due to the problem being ill-posed.…”

Section: Figsupporting

confidence: 82%

“…It has been successfully applied to the seismological inference of coronal loop parameters from the observations of damped kink oscillations (e.g., Arregui et al 2013aArregui & Asensio Ramos 2011). Arregui et al (2013b) describe a version of the seismological inversion technique using the Gaussian and exponential damping regimes based on Bayesian analysis, while Arregui & Asensio Ramos (2014) consider Bayesian analysis of the ill-posed case i.e. the exponential damping regime only.…”

Section: Bayesian Inferencementioning

confidence: 99%

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

Pascoe

Anfinogentov

Nisticò

et al. 2017

A&A

101

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(2017) Coronal loop seismology using damping of standing kink oscillations by mode coupling II. additional physical effects and Bayesian analysis. Astronomy and Astrophysics, 600 . A78. Permanent WRAP URL:http://wrap.warwick.ac.uk/85278 Copyright and reuse:The Warwick Research Archive Portal (WRAP) makes this work by researchers of the University of Warwick available open access under the following conditions. Copyright © and all moral rights to the version of the paper presented here belong to the individual author(s) and/or other copyright owners. To the extent reasonable and practicable the material made available in WRAP has been checked for eligibility before being made available.Copies of full items can be used for personal research or study, educational, or not-for-profit purposes without prior permission or charge. Provided that the authors, title and full bibliographic details are credited, a hyperlink and/or URL is given for the original metadata page and the content is not changed in any way. Publisher's statement:Reproduced with permission from Astronomy & Astrophysics, © ESO A note on versions:The version presented here may differ from the published version or, version of record, if you wish to cite this item you are advised to consult the publisher's version. Please see the 'permanent WRAP URL' above for details on accessing the published version and note that access may require a subscription. ABSTRACTContext. The strong damping of kink oscillations of coronal loops can be explained by mode coupling. The damping envelope depends on the transverse density profile of the loop. Observational measurements of the damping envelope have been used to determine the transverse loop structure which is important for understanding other physical processes such as heating.Aims. The general damping envelope describing the mode coupling of kink waves consists of a Gaussian damping regime followed by an exponential damping regime. Recent observational detection of these damping regimes has been employed as a seismological tool. We extend the description of the damping behaviour to account for additional physical effects, namely a time-dependent period of oscillation, the presence of additional longitudinal harmonics, and the decayless regime of standing kink oscillations. Methods. We examine four examples of standing kink oscillations observed by the Atmospheric Imaging Assembly (AIA) onboard the Solar Dynamics Observatory (SDO). We use forward modelling of the loop position and investigate the dependence on the model parameters using Bayesian inference and Markov Chain Monte Carlo (MCMC) sampling. Results. Our improvements to the physical model combined with the use of Bayesian inference and MCMC produce improved estimates of model parameters and their uncertainties. Calculation of the Bayes factor also allows us to compare the suitability of different physical models. We also use a new method based on spline interpolation of the zeroes of the oscillation to accurately describe the background trend of the osci...

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Section: Figsupporting

confidence: 82%

Section: Bayesian Inferencementioning

confidence: 99%

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

Pascoe

Anfinogentov

Nisticò

et al. 2017

A&A

101

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“…Then, the observed values and the theoretical/numerical predictions can be compared by adopting a likelihood of the form (2011), we make use of the basic definition of marginal posteriors, by performing the required integrals over the parameter space. This was first done by Arregui & Asensio Ramos (2014) to infer the density contrast and transverse inhomogeneity length scale from measured damping ratio values. As shown by these authors, although the classic onedimensional curves in the parameter space point to an infinite number of equally valid solutions, not all of them are equally probable.…”

Section: Parameter Inferencementioning

confidence: 99%

“…By assuming a density contrast between the interior of the loop and the external corona, estimates for the transverse inhomogeneity length scale can be obtained. Recent expansions of this idea have considered the Bayesian inversion of both density contrast and transverse inhomogeneity length scale by making use of different damping regimes (Arregui et al 2013) or the computation of their marginal posteriors from observed damping ratios (Arregui & Asensio Ramos 2014). In these studies, the density structuring was arbitrarily prescribed.…”

Section: Introductionmentioning

confidence: 99%

Model Comparison for the Density Structure Across Solar Coronal Waveguides

Arregui

Soler

Ramos

2015

ApJ

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The spatial variation of physical quantities, such as the mass density, across solar atmospheric waveguides governs the timescalesand spatial scales for wave damping and energy dissipation. The direct measurement of the spatial distribution of density, however, is difficult, and indirect seismology inversion methods have been suggested as an alternative. We applied Bayesian inference, model comparison, and model-averaging techniques to the inference of the cross-field density structuring in solar magnetic waveguides using information on periods and damping times for resonantly damped magnetohydrodynamic transverse kink oscillations. Three commonly employed alternative profiles were used to model the variation of the mass density across the waveguide boundary. Parameter inference enabled us to obtain information on physical quantities such as the Alfvén travel time, the density contrast, and the transverse inhomogeneity length scale. The inference results from alternative density models were compared and their differences quantified. Then, the relative plausibility of the considered models was assessed by performing model comparison. Our results indicate that the evidence in favor of any of the three models is minimal, unless the oscillations are strongly damped. In such a circumstance, the application of model-averaging techniques enables the computation of an evidence-weighted inference that takes into account the plausibility of each model in the calculation of a combined inversion for the unknown physical parameters.

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“…In this paper, we apply this method to observational data from the Atmospheric Imaging Assembly (AIA) of the Solar Dynamics Observatory (SDO). Arregui et al (2013) employed a version of the inversion technique using Bayesian analysis of the two fitted damping times to constrain the loop parameters and errors when the problem is well-posed, while Arregui & Asensio Ramos (2014) considered Bayesian analysis to derive structuring information even for the ill-posed case. Tomczyk et al (2007) discovered ubiquitous transverse velocity perturbations propagating in the corona.…”

Section: Introductionmentioning

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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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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Determination of the cross-field density structuring in coronal waveguides using the damping of transverse waves

Cited by 20 publications

References 29 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

Model Comparison for the Density Structure Across Solar Coronal Waveguides

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

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