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Astron. Astrophys. 363, 306-310 (2000)


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Oscillations and running waves observed in sunspots *

II. Photospheric waves

A.A. Georgakilas 1,2, E.B. Christopoulou 1,3 and S. Koutchmy 4

1 Thessalias 13, 13231 Petroupoli, Athens, Greece (ageorgakilas, echristopoulou@solar.stanford.edu)
2 Solar Astronomy, California Institute of Technology, Pasadena, CA 91125, USA (ageorg@caltech.edu)
3 Electronics Laboratory, University of Patras, 26110 Patras, Greece (echris@physics.upatras.gr)
4 Institut d'Astrophysique de Paris, CNRS, 98 bis boulevard Arago, 75014 Paris, France (koutchmy@iap.fr)

Received 20 July 2000 / Accepted 11 August 2000

Abstract

To continue our study of waves related to sunspots in the photosphere, we analyzed CCD, high resolution sunspot observations obtained in the Fe I 557.6 nm line. We produced "time slice images" which reveal inward slow propagating waves in the photospheric penumbra and outward propagating waves in the area around the sunspot. The phase velocity of the waves is near 0.5 km s-1 in both cases and their horizontal wavelength about 2500 km. The waves could be related either to solar p-modes or to the subphotospheric layer large-scale convection.

Key words: Sun: sunspots – Sun: oscillations

* Based on observations performed on the NSO/SPO Dunn's Solar Telescope (DST)

Send offprint requests to: A.A. Georgakilas

© European Southern Observatory (ESO) 2000

Online publication: December 5, 2000

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