Pascoe, D. J. (David J.), Nakariakov, Valery M. and Arber, T. D.. (2007) Sausage oscillations of coronal loops. Astronomy & Astrophysics, Vol.461 (No.3). pp. 1149-1154. ISSN 0004-6361

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Abstract

Aims. Analytical theory predicts the existence of trapped global (or fundamental) sausage fast magnetoacoustic modes in thick and dense coronal loops only, with the periods estimated as the ratio of double the loop length and the Alfvén speed outside the loop. We extend this study to the leaking regime, considering global sausage modes of long loops with small density contrasts. Methods. Anti-symmetric fast magnetoacoustic perturbations (sausage, or m = 0 modes) of a low β plasma slab with the symmetric Epstein profile of plasma density are modelled numerically. Results. It was found that long loops with sufficiently small density contrast can support global sausage leaky modes of detectable quality. The periods of the leaky modes are found to be approximately determined by the loop length and the external Alfvén speed. If the loop length can be estimated from imaging observations, the observed period of this mode provides us with the information about the Alfvén speed outside the loop. For typical flaring coronal loops, the estimated periods of the global sausage modes are about 5−60 s.

Item Type:	Journal Article
Subjects:	Q Science > QB Astronomy
Divisions:	Faculty of Science > Physics
Library of Congress Subject Headings (LCSH):	Sun -- Loop prominences, Sun -- Corona, Solar flares, Solar oscillations, Magnetohydrodynamics
Journal or Publication Title:	Astronomy & Astrophysics
Publisher:	EDP Sciences
ISSN:	0004-6361
Date:	January 2007
Volume:	Vol.461
Number:	No.3
Page Range:	pp. 1149-1154
Identification Number:	10.1051/0004-6361:20065986
Status:	Peer Reviewed
Access rights to Published version:	Open Access
Funder:	Particle Physics and Astronomy Research Council (Great Britain) (PPARC)
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URI:	http://wrap.warwick.ac.uk/id/eprint/3474

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