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

Abstract

(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...

A statistical study of the inferred transverse density profile of coronal loop threads observed with SDO/AIA

“…We follow the model comparison procedure based on Bayesian inference and Markov chain Monte Carlo (MCMC) sampling described in Pascoe et al (2017a) and applied to a coronal loop intensity profile in Pascoe et al (2017b).…”

“…where the evidences, P pD|Mq are calculated as described in Pascoe et al (2017a). To define evidence thresholds the natural logarithm of this factor, i.e.…”

“…This work lead to the confirmation of the presence of non-exponential damping envelopes of some of the oscillations studied (Pascoe et al 2016b). This can be attributed to the damping profile proposed in Pascoe et al (2012Pascoe et al ( , 2013, which has subsequently been used to perform seismology, including the use of Bayseian model comparison (Pascoe et al 2016a(Pascoe et al , 2017a. In Pascoe et al (2017b) the result of this seismology was compared to density profiles estimated from the EUV intensity for one coronal loop.…”

“…In addition, the structuring parameters with the greatest evidence are obtained for each density model. Our model comparison approach, described in Section 3, is the same as that described in Pascoe et al (2017a).…”

Seismology of contracting and expanding coronal loops using damping of kink oscillations by mode coupling

“…The seismological method proposed by Pascoe et al (2013a) was first used to calculate the transverse density profile of coronal loops by Pascoe et al (2016b), and further developed by Pascoe et al (2017a) to account for additional physical effects including a time-dependent loop length and the presence of the second and third parallel harmonics of the kink mode. The seismological estimate of the inhomogeneous layer width of Loop #3 in Pascoe et al (2017a) was found to be consistent with an independent estimate based on forward modelling of the transverse intensity profile (Pascoe et al 2017b), while a statistical study of 233 coronal loops found that 75% exhibit evidence for an inhomogeneous layer (Goddard et al 2017). …”