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Astron. Astrophys. 342, 863-866 (1999)


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Research Note

Leaky and resonantly damped flux tube modes reconsidered

H. Stenuit 1, W.J. Tirry *  1, R. Keppens 2 and M. Goossens 1

1 Centre for Plasma Astrophysics, K.U. Leuven, Celestijnenlaan 200B, B-3001 Heverlee, Belgium
2 FOM-Institute for Plasma Physics `Rijnhuizen', P.O. Box 1207, 3430 BE Nieuwegein, The Netherlands

Received 20 April 1998 / Accepted 3 November 1998

Abstract

In this research note the results for the eigenfrequencies of the uniform and non-uniform magnetic flux tubes of Stenuit et al. (1998) are reconsidered. In that paper it is shown that the eigenfrequencies may have a damping rate due to two mechanisms causing a loss of energy. In non-uniform flux tubes the eigenmodes can be damped by resonant absorption. The other mechanism is leakage of wave energy into the surroundings, which can occur for both uniform and non-uniform flux tubes.

We point out that the dispersion relations obtained by Stenuit et al. are correct for leaky and undamped non-leaky modes, but are not correct for resonantly damped non-leaky modes.

Key words: Magnetohydrodynamics (MHD) – Sun: oscillations – Sun: photosphere – Sun: sunspots

* Research Assistant of the F.W.O.-Vlaanderen

Send offprint requests to: H. Stenuit

© European Southern Observatory (ESO) 1999

Online publication: February 23, 1999

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