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Issue A&A
Volume 414, Number 2, February I 2004
Page(s) L25 - L28
Section Letters
DOI http://dx.doi.org/10.1051/0004-6361:20031738



A&A 414, L25-L28 (2004)
DOI: 10.1051/0004-6361:20031738

Letter

Acoustic oscillations in solar and stellar flaring loops

V. M. Nakariakov1, D. Tsiklauri1, A. Kelly1, T. D. Arber1 and M. J. Aschwanden2

1  Physics Department, University of Warwick, Coventry, CV4 7AL, UK
2  Lockheed Martin, Advanced Technology Center Solar & Astrophysics Lab, Dept. L9-41, Bldg. 252, 3251 Hanover Street, Palo Alto, CA 94304, USA

(Received 20 November 2003 / Accepted 11 December 2003)

Abstract
Evolution of a coronal loop in response to an impulsive energy release is numerically modelled. It is shown that the loop density evolution curves exhibit quasi-periodic perturbations with the periods given approximately by the ratio of the loop length to the average sound speed, associated with the second standing harmonics of an acoustic wave. The density perturbations have a maximum near the loop apex. The corresponding field-aligned flows have a node near the apex. We suggest that the quasi-periodic pulsations with periods in the range 10-300 s, frequently observed in flaring coronal loops in the radio, visible light and X-ray bands, may be produced by the second standing harmonic of the acoustic mode.


Key words: Sun: flares -- Sun: oscillations -- Sun: corona -- stars: flare -- stars: oscillations -- stars: coronae

Offprint request: V. M. Nakariakov, valery@astro.warwick.ac.uk




© ESO 2004


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