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

Pascoe, D.J., Russell, A.J.B., Anfinogentov, S.A., Simões, P.J.A. , Goddard, C.R., Nakariakov, V.M. and Fletcher, L. (2017) Seismology of contracting and expanding coronal loops using damping of kink oscillations by mode coupling. Astronomy and Astrophysics, 607, A8. (doi:10.1051/0004-6361/201730915)

Pascoe, D.J., Russell, A.J.B., Anfinogentov, S.A., Simões, P.J.A. , Goddard, C.R., Nakariakov, V.M. and Fletcher, L. (2017) Seismology of contracting and expanding coronal loops using damping of kink oscillations by mode coupling. Astronomy and Astrophysics, 607, A8. (doi:10.1051/0004-6361/201730915)

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Abstract

Aims. We extend recently developed seismological methods to analyse oscillating loops which feature a large initial shift in the equilibrium position and investigate additional observational signatures related to the loop environment and oscillation driver. Methods. We model the motion of coronal loops as a kink oscillation damped by mode coupling, accounting for any change in loop length and the possible presence of parallel harmonics in addition to the fundamental mode. We apply our model to a loop which rapidly contracts due to a post-flare implosion (SOL2012-03-09) and a loop with a large lateral displacement (SOL2012-10-20). Results. The seismological method is used to calculate plasma parameters of the oscillating loops including the transverse density profile, magnetic field strength, and phase mixing timescale. For SOL2012-03-09 the period of oscillation has a linear correlation with the contracting motion and suggests the kink speed remains constant during the oscillation. The implosion excitation mechanism is found to be associated with an absence of additional parallel harmonics. Conclusions. The improved Bayesian analysis of the coronal loop motion allows for accurate seismology of plasma parameters and the evolution of the period of oscillation compared with the background trend can be used to distinguish between loop motions in the plane of the loop or perpendicular to it. The seismologically inferred kink speed and density contrast imply sub-Alfvenic (MA = 0.16 ± 0.03) propagation of the magnetic reconfiguration associated with the implosion, as opposed to triggering by a wave propagating at the Alfven speed.

Item Type:Articles
Keywords:Magnetohydrodynamics (MHD), sun: atmosphere, sun: corona, sun: magnetic fields, sun: oscillations, waves.
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:Simoes, Dr Paulo and Fletcher, Professor Lyndsay
Authors: Pascoe, D.J., Russell, A.J.B., Anfinogentov, S.A., Simões, P.J.A., Goddard, C.R., Nakariakov, V.M., and Fletcher, L.
Subjects:Q Science > QB Astronomy
Q Science > QC Physics
College/School:College of Science and Engineering > School of Physics and Astronomy
Research Group:Astronomy and Astrophysics
Journal Name:Astronomy and Astrophysics
Publisher:EDP Sciences
ISSN:0004-6361
ISSN (Online):1432-0746
Published Online:17 August 2017
Copyright Holders:Copyright © 2017 EDP Sciences
First Published:First published in Astronomy and Astrophysics 607: A8
Publisher Policy:Reproduced in accordance with the publisher copyright policy

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Project CodeAward NoProject NamePrincipal InvestigatorFunder's NameFunder RefLead Dept
631581Consolidated grant in solar and astrophysical plasmasLyndsay FletcherScience & Technology Facilities Council (STFC)ST/L000741/1S&E P&A - PHYSICS & ASTRONOMY