In 1994 we performed observations at the German Vacuum Tower Telescope at the Observatorio del Teide (Tenerife) using a polarimeter in front of a two-dimensional imaging spectrometer with a tunable narrow-band Fabry-Perot interferometer. We observed the main sunspot of the active region NOAA 7577 and measured the Doppler line shift and the Zeeman splitting of the line Fe I 6173 AA. The data show significant power of velocity and magnetic field oscillations in period bands at 3 min and 5 min, a strong coherence of the velocity and magnetic field oscillations, and a clear dependence of the phase difference on the period and on the position, pointing out a longitudinal character of the oscillations.
New Eyes to See Inside the Sun and Stars
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