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In this paper we analyze the distribution of magnetic strength ratios (MSR) across the solar disk using magnetograms in different spectral lines from the same observatory (Mount Wilson Observatory (MWO) and Sayan Observatory (SO)), magnetograms in the same line from different observatories (MWO, SO, Wilcox Solar Observatory (WSO)), and in different spectral lines from different observatories (the three observatories mentioned above, the National Solar Observatory/Kitt Peak (KP) and Michelson Doppler Imager (MDI) on board Solar and Heliospheric Observatory (SoHO)). We find peculiarities in some combinations of data sets. Besides the expected MSR center-to-limb variations, there is an equatorto-pole asymmetry, especially in the near-limb areas. Therefore, it is generally necessary to use 2D matrices of correction coefficients to reduce one kind of observation into another one.

High‐frequency heating of the ionosphere is effective for generating extremely low frequencies (ELF, 3–3000 Hz) through modulation of the auroral electrojet current. While the amplitudes of the resulting ELF waves depend on the auroral electrojet current strength, the polarization of their horizontal magnetic field remains relatively stable. In this work, we determined that at the distance of several wavelengths from an ionospheric ELF source created by two HF heating waves separated by an ELF frequency, polarization parameters are influenced by the Earth‐ionosphere waveguide. Previous experiments in the vicinity of the ionospheric ELF source have determined that the right‐hand polarization of the magnetic field measured at the ground typically prevails, whereas in this paper we demonstrate that at the distance of 660 km to the east of the European Incoherent Scatter, a circular left‐hand polarization dominates. We interpret this effect as a result of “trapping” of the left‐hand mode between the upper and lower boundaries of the Earth‐ionosphere waveguide, while the right‐hand or whistler mode leaks into the ionosphere.

This paper presents some results of observations of the mean magnetic field of the Sun as a star (SMMF) at the Sayan Observatory during 1982-1984. A description of the instrument is given, as well as some major points in the technique of data acquisition and treatment such as calibration, zero-level control, etc. The comparison of a new SMMF series with observations from the Wilcox Solar Observatory showed a high correlation between the two series (p = 0.88) but with a rather great difference in amplitudes. We discuss time variations of SMMF, both long-term caused by the magnetic field evolution with the activity cycle and those of shorter time-scales caused by solar rotation.

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One of the most important problems of modern solar physics is the observation of the small-scale structure of the solar atmosphere at various heights (including the chromosphere and corona) in different spectral lines. Such observations can be made only with large solar telescopes whose main mirror has a diameter of at least 3 m. Currently, several large solar telescopes are under construction or development in the world. In 2013 in Russia, the work began on the development of a national large solar telescope with a mirror 3 m in diameter (LST-3), which is a part (subproject) of the National Heliogeophysical Complex of the Russian Academy of Sciences. The telescope is planned to be located in the Sayan Solar Observatory at an altitude of more than 2000 m. The choice was made in favor of the classic axisymmetric Gregory optical layout on an alt-azimuth mount. The scientific equipment of LST-3 will consist of several systems of narrow-band tunable filters and spectrographs for various wave ranges. The equipment will be placed both in the main coude focus on a rotating platform and in the Nasmyth focus. To achieve a diffraction resolution, high-order adaptive optics (AO) will be used. It is assumed that with a certain modification of the optical configuration, LST-3 will work as a 0.7 m mirror coronograph in near infrared lines and can also be used for observing astrophysical objects in the nighttime.

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