Pascoe, D. J. (David J.), Nakariakov, V. M. (Valery M.), Arber, T. D. and Murawski, K. (2009) Sausage oscillations in loops with a non-uniform cross-section. Astronomy & Astrophysics, Vol.494 (No.3). pp. 1119-1125. doi:10.1051/0004-6361:200810541 ISSN 0004-6361.

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Abstract

Context. Flaring coronal loops are often observed in microwave and sometimes in soft X-rays, as extended structures of variable cross-section or width. The quasi-periodic pulsations associated with flaring coronal loops have been interpreted in terms of standing, fast sausage magnetoacoustic modes and suggested for the diagnostics of the magnetic field outside the oscillating loop.
Aims. We investigate the effects of a non-uniform cross-section on a coronal loop with respect to the standing sausage modes it supports.
Methods. Numerical simulations of standing sausage modes are performed for a straight, zero-β coronal loop with a varying crosssection. The global sausage mode and higher harmonics are considered, and simulations were performed for a range of density contrast ratios and loop divergence parameter. We consider modifications of the period of oscillation and the spatial profile of the standing
modes.
Results. As the loop divergence parameter increases, the period of the standing modes decreases. The fractional change period is independent of the density contrast ratio. The spatial profiles of the standing modes are modified by the cross-section inhomogeneity,but this effect is too weak to be observable by modern instruments. For the global sausage mode, the cross-section radius divergence
by a factor of 2 is found to cause the decrease in the period of about 5%.

Item Type:	Journal Article
Subjects:	Q Science > QB Astronomy
Divisions:	Faculty of Science, Engineering and Medicine > Science > Physics
Library of Congress Subject Headings (LCSH):	Sun -- Loop prominences, Solar oscillations, Solar flares, Sun -- Corona, Magnetohydrodynamics
Journal or Publication Title:	Astronomy & Astrophysics
Publisher:	EDP Sciences
ISSN:	0004-6361
Official Date:	February 2009
Dates:	Date Event February 2009 Published
Volume:	Vol.494
Number:	No.3
Page Range:	pp. 1119-1125
DOI:	10.1051/0004-6361:200810541
Status:	Peer Reviewed
Access rights to Published version:	Open Access (Creative Commons)
Funder:	Particle Physics and Astronomy Research Council (Great Britain) (PPARC), Science and Technology Facilities Council (Great Britain) (STFC), Poland. Ministerstwo Nauki i Szkolnictwa Wyższego [Ministry of Science and Higher Education] (MNiSW), International Space Science Institute (ISSI)

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