Volume 461, Number 3, January III 2007
|Page(s)||1149 - 1154|
|Published online||11 October 2006|
Sausage oscillations of coronal loops
Physics Department, University of Warwick, Coventry, CV4 7AL, UK e-mail: D.J.Pascoe@warwick.ac.uk
Accepted: 29 September 2006
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 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.
Key words: Sun: corona / Sun: oscillations / Sun: flares / magnetohydrodynamics (MHD)
© ESO, 2007
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.