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Issue A&A
Volume 430, Number 3, February II 2005
Page(s) L65 - L68
Section Letters
DOI http://dx.doi.org/10.1051/0004-6361:200400133



A&A 430, L65-L68 (2005)
DOI: 10.1051/0004-6361:200400133

Letter

Transverse waves in a post-flare supra-arcade

E. Verwichte, V. M. Nakariakov and F. C. Cooper

Department of Physics, University of Warwick, Coventry CV4 7AL, UK
    e-mail: Erwin.Verwichte@warwick.ac.uk

(Received 30 September 2004 / Accepted 10 December 2004 )

Abstract
Observations of propagating transverse waves in an open magnetic field structure with the Transition Region And Coronal Explorer (TRACE) are presented. Waves associated with dark tadpole-like sunward moving structures in the post-flare supra-arcade of NOAA active region 9906 on the 21 ${{\rm st}}$ of April 2002 are analysed. They are seen as quasi-periodic transverse displacements of the dark tadpole tails, with periods in the range of 90-220 s. Their phase speeds and displacement amplitudes decrease as they propagate sunwards. At heights of 90 and 60 Mm above the post-flare loop footpoints the phase speeds are in the ranges 200-700 km s -1 and 90-200 km s -1 respectively. Furthermore, for consecutive tadpoles the phase speeds decrease and periods increase as a function of time. The waves are interpreted as propagating fast magnetoacoustic kink waves guided by a vertical, evolving, open structure.


Key words: Sun: oscillations -- magnetohydrodynamics (MHD)




© ESO 2005


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