Development modulationless measuring magnetic fields and differential velocities at Sayan observatory

In this paper we consider the possibility of modulationless measuring the magnetic-field strength and the differential line-of-sight velocity, based on using a diffraction spectrograph and multichannel CCD photodetectors. The optical system for implementing the method is described. Results of trial observations are presented. When measuring the differential velocity, the spectrograph’s inherent noise is reduced by factors of 35–40. It becomes possible to measure the longitudinal magnetic-field strength in a single exposure even if the CCD array is used. This can be particularly attractive when reducing the influence of atmospheric instabilities on the result of magnetic-field measurement using CCD arrays

Flows and oscillations in sunspot penumbra

In observations of penumbra oscillations there is the challenging problem of separating the oscillations associated with Evershed flows from those of a different nature. The authors used the differential method which is best suited to this problem as it can be used to filter out the wave motions in the direction and wavelength already at the stage of observation. Our findings indicate that, in addition to the 10–12 min periods, periods near 30–35 minutes are present in the velocity variations of Evershed flows. Furthermore, the possible candidates for this role are the 8 min oscillations, which we have also observed at two height levels of sunspot penumbra