A method of directly measuring Doppler shifts and the Zeeman effect from digital optical spectrograms of the sun and the long-period oscillations of sunspots

This paper describes a method developed and used at the Main (Pulkovo) Observatory, Russian Academy of Sciences, for recording Doppler shifts, as well as the broadening's of spectral lines caused by their Zeeman splitting, from digital optical spectrograms of active regions of the sun. It is shown that, in fairly prolonged (more than 4 h) continuous observations, long-period variations of the line-of-sight velocities and the magnetic field, with a characteristic period of about 80 min, are detected in sunspots and in magnetic elements of the surrounding photosphere. These variations are interpreted as vertical or line-of-sight oscillations of the entire spot (or the magnetic element) as a whole, caused by perturbing action from the surrounding turbulent medium (the photosphere and the convective zone). (C) 2008 Optical Society of America.