POSSIBILITIES OF ASTRONOMICAL AND ECOLOGICAL RESEARCH WITH HORIZONTAL SOLAR TELESCOPE OF AO KNU – AN OBJECT OF NATIONAL PROPERTY
Authors:   Taras Shevchenko National University of Kyiv, Kyiv, Ukraine, LOZITSKY Vsevolod 
Published: November 2024

B a c k g r o u n d . The appearance in recent years of large solar telescopes, which achieve a spatial resolution of up to 50 km on the Sun, exacerbates the question of the feasibility of using much smaller solar telescopes. The presented work argues the thesis that even medium and relatively small solar telescopes can provide important information that corresponds to the current level of science in the fields of astronomy and environmental research. This is due to the fact that for spectral-polarization studies of active processes on the Sun, not only direct spatial resolution is critically important, but also spectral resolution and the width of simultaneous spectrum registration. At the same time, high spectral resolution can to some extent compensate for insufficiently high spatial resolution. The purpose of the presented work was to highlight specific methodological approaches and results in the specified scientific directions using the example of the horizontal solar telescope of the Astronomical Observatory of Taras Shevchenko National University of Kyiv (hereinafter – HST AO KNU), which recently received the status of an object of national heritage. M e t h o d s . The spectral-polarization method was mainly used for analysis of observational data in many spectral lines formed in the “photosphere-lower corona” height range. The local characteristics of the magnetic fields on the Sun were determined both by the direct method (for sunspots) and by analyzing subtle effects in the distant wings and the nearby spectral continuum of H-alpha and D3 helium lines (for solar flares). In the latter case, the local characteristics of the magnetic field and the velocity field were also estimated by simulation. R e s u l t s . According to the observations with the HST of AO KNU, a reliable circular polarization of the opposite sign was found in the far wings of H-alpha and D3 HeI lines in two powerful solar flares of X class, which most likely indicates magnetic fields of 105 G range. To justify this interpretation, theoretical features of the Paschen-Back effect in magnetic fields up to 100 kG were investigated by Ivan Yakovkin. It turned out that at such fields the spectral width of the splitting components of the D3 line is relatively small, 0.3 Å, while the width of the observed peaks is sometimes much larger, which may indicate a significant dispersion of the magnetic field intensities in the flares. On the basis of model calculations, it is shown that in some cases an alternative explanation of the observed data is possible, which includes much weaker magnetic fields (5.5-7.1 kG), but significant macroscopic velocities of different signs, at the level of 50-60 km s -1 . C o n c l u s i o n s . We conclude that spectral-polarization observations of active processes on the Sun using the HST of AO KNU have the greatest value when they are carried out in the monitoring mode and with the aim of recording extremely powerful manifestations of solar activity. It was shown that magnetic fields of 105 G range are possible in solar flares even in the lower solar corona till heights of 10-20 Mm, which is of considerable interest for the MHD theory of concentrated fields in the solar atmosphere