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

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Goddard, Christopher R., Pascoe, D. J. (David J.), Anfinogentov, Sergey and Nakariakov, V. M. (Valery M.) (2017) A statistical study of the inferred transverse density profile of coronal loop threads observed with SDO/AIA. Astronomy & Astrophysics, 605 . A65. doi:10.1051/0004-6361/201731023

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Official URL: http://dx.doi.org/10.1051/0004-6361/201731023

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Abstract

Aims. We carry out a statistical study of the inferred coronal loop cross-sectional density profiles using extreme ultraviolet (EUV) imaging data from the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory (SDO).
Methods. We analysed 233 coronal loops observed during 2015/2016. We consider three models for the density profile; the step function (model S ), the linear transition region profile (model L), and a Gaussian profile (model G). Bayesian inference is used to compare the three corresponding forward modelled intensity profiles for each loop. These are constructed by integrating the square of the density from a cylindrical loop cross section along the line of sight, assuming an isothermal cross section, and applying the instrumental point spread function.
Results. Calculating the Bayes factors for comparisons between the models, it was found that in 47 % of cases there is very strong evidence for model L over model S and in 45 % of cases very strong evidence for model G over S . Using multiple permutations of the Bayes factor the favoured density profile for each loop was determined for multiple evidence thresholds. There were a similar number of cases where model L or G are favoured, showing evidence for inhomogeneous layers and constantly varying density cross sections, subject to our assumptions and simplifications.
Conclusions. For sufficiently well resolved loop threads with no visible substructure it has been shown that using Bayesian inference and the observed intensity profile we can distinguish between the proposed density profiles at a given AIA wavelength and spatial resolution. We have found very strong evidence for inhomogeneous layers, with model L being the most general, and a tendency towards thicker or even continuous layers.

Item Type: Journal Article
Subjects: Q Science > QB Astronomy
Q Science > QC Physics
Divisions: Faculty of Science > Physics
Library of Congress Subject Headings (LCSH): Sun--Corona, Sun--Loop prominences, Sun--Loop prominences--Density, Solar oscillations--Statistics
Journal or Publication Title: Astronomy & Astrophysics
Publisher: EDP Sciences
ISSN: 0004-6361
Official Date: 11 September 2017
Dates:
DateEvent
11 September 2017Published
2 June 2017Accepted
Volume: 605
Article Number: A65
DOI: 10.1051/0004-6361/201731023
Status: Peer Reviewed
Publication Status: Published
Funder: European Research Council (ERC)
Grant number: 321141

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