Hindman, B.W. and Jain, R. orcid.org/0000-0002-0080-5445 (2018) A Novel Approach to Resonant Absorption of the Fast MHD Eigenmodes of a Coronal Arcade. Astrophysical Journal, 858. 6. ISSN 0004-637X
Abstract
The arched eld lines forming coronal arcades are often observed to undulate as magne- tohydrodynamic (MHD) waves propagate both across and along the magnetic eld. These waves are most likely a combination of resonantly coupled fast magnetoacoustic waves and Alfv\' en waves. The coupling results in resonant absorption of the fast waves, converting fast wave energy into Alfv\' en waves. The fast eigenmodes of the arcade have proven difficult to compute or derive analytically, largely because of the mathematical complexity that the coupling introduces. When a traditional spectral decomposition is employed, the discrete spectrum associated with the fast eigenmodes is often subsumed into the continuous Alfv \'en spectrum. Thus fast eigenmodes, become collective modes or quasi-modes. Here we present a spectral decomposition that treats the eigenmodes as having real frequencies but complex wavenumbers. Using this procedure we derive dispersion relations, spatial damping rates, and eigenfunctions for the resonant, fast eigenmodes of the arcade. We demonstrate that resonant absorption introduces a fast mode that would not exist otherwise. This new mode is heavily damped by resonant absorption, only travelling a few wavelengths before losing most of its energy.
Metadata
Item Type: | Article |
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Authors/Creators: |
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Copyright, Publisher and Additional Information: | © 2018. The American Astronomical Society. Reproduced in accordance with the publisher's self-archiving policy. |
Dates: |
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Institution: | The University of Sheffield |
Academic Units: | The University of Sheffield > Faculty of Science (Sheffield) > School of Mathematics and Statistics (Sheffield) |
Depositing User: | Symplectic Sheffield |
Date Deposited: | 03 Apr 2018 11:10 |
Last Modified: | 04 Jun 2018 14:46 |
Published Version: | https://doi.org/10.3847/1538-4357/aab9b1 |
Status: | Published |
Publisher: | American Astronomical Society |
Refereed: | Yes |
Identification Number: | 10.3847/1538-4357/aab9b1 |
Open Archives Initiative ID (OAI ID): | oai:eprints.whiterose.ac.uk:129074 |