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Identification of linear slow sausage waves in magnetic pores

Published online by Cambridge University Press:  01 September 2007

I. Dorotovič ,
R. Erdélyi  and
V. Karlovský
I. Dorotovič
Affiliation:
Slovak Central Observatory, P. O. Box 42, SK-94701 Hurbanovo, Slovak Republic; Grupo de Astrofísica da Universidade de Coimbra, Coimbra, Portugal email: dorotovic@suh.sk
R. Erdélyi
Affiliation:
Solar Physics & Space Plasma Research Centre (SP2RC), Dept. of Applied Mathematics, University of Sheffield, Hicks Building, Hounsfield Road, Sheffield, S3 7RH (England)UK email: robertus@sheffield.ac.uk
V. Karlovský
Affiliation:
Hlohovec Observatory and Planetarium, Sládkovičova 41, SK-92001 Hlohovec, Slovak Republic, email: astrokar@hl.cora.sk
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Abstract

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The analysis of an 11-hour series of high resolution white light observations of a large pore in the sunspot group NOAA 7519, observed on 5 June 1993 with the Swedish Vacuum Solar Telescope at La Palma on Canary Islands, has been recently described by Dorotovič et al. (2002). Special attention was paid to the evolution of a filamentary region attached to the pore, to horizontal motions around the pore, and to small-scale morphological changes. One of the results, relevant to out work here, was the determination of temporal area evolution of the studied pore where the area itself showed a linear trend of decrease with time at an average rate of −0.23 Mm2h−1 during the entire observing period. Analysing the time series of the are of the pore, there is strong evidence that coupling between the solar interior and magnetic atmosphere can occur at various scales and that the referred decrease of the area may be connected with a decrease of the magnetic field strength according to the magnetic field-to-size relation. Periods of global acoustic, e.g. p-mode, driven waves are usually in the range of 5–10 minutes, and are favourite candidates for the coupling of interior oscillations with atmospheric dynamics. However, by assuming that magneto-acoustic gravity waves may be there too, and may act as drivers, the observed periodicities (frequencies) are expected to be much longer (smaller), falling well within the mMHz domain. In this work we determine typical periods of such range in the area evolution of the pore using wavelet analysis. The resulted periods are in the range of 20–70 minutes, suggesting that periodic elements of the temporal evolution of the area of this studied pore could be linked to, and considered as, observational evidence of linear low-frequency slow sausage (magneto-acoustic gravity) waves in magnetic pores. This would give us further evidence on the coupling of global solar oscillations to the overlaying magnetic atmosphere.

Keywords

magnetic fields — MHD — Sun: photosphere
Type
Contributed Papers
Information
Proceedings of the International Astronomical Union , Volume 3 , Symposium S247: Waves & Oscillations in the Solar Atmosphere: Heating and Magneto-Seismology , September 2007 , pp. 351 - 354
Copyright
Copyright © International Astronomical Union 2008

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