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Astron. Astrophys. 346, 633-640 (1999)

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Center-to-limb variation of the solar oscillation

New results from MDI data

W. Schmidt, M. Stix and H. Wöhl

Kiepenheuer-Institut für Sonnenphysik, Schöneckstrasse 6, D-79104 Freiburg, Germany (wolfgang, stix, hw@kis.uni-freiburg.de)

Received 25 August 1998 / Accepted 19 March 1999


Using 17 hours of full-disk MDI Doppler data we have investigated the center-to-limb variation of the oscillatory wave spectrum of the solar photosphere. Power distributions in the [FORMULA]-plane are calculated for fields of [FORMULA] on the Sun, centered at every [FORMULA] heliographic latitude. From the center-to-limb variation of the power in the f mode and the lowest 7 p modes we obtain information about the mean inclination of the oscillatory velocity vector with respect to the vertical direction. We find qualitative agreement with a model of adiabatic waves in an isothermal atmosphere, but generally the solar oscillations appear to be less inclined than the model oscillations. We find no indication for the existence of horizontal sound waves on the Sun.

Key words: Sun: oscillations

Send offprint requests to: W. Schmidt

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© European Southern Observatory (ESO) 1999

Online publication: May 21, 1999