Observation of the Solar Eclipse on October 25, 2022 on Radio Telescopes of the Institute of Applied Astronomy, Russian Academy of Sciences (First Results)

• Published in: Geomagnetism and Aeronomy 2023-12, Vol.63 (7), p.1015-1023
• Main Authors: Ivanov, D. V., Rakhimov, I. A., D’akov, A. A., Il’in, G. N., Topchilo, N. A., Peterova, N. G., Ipatov, A. V., Andreeva, T. C., Khvostov, E. Yu, Bikov, V. Yu
• Format: Article
• Language: English
• Subjects: Astronomy; Brightness temperature; Circular polarization; Earth and Environmental Science; Earth Sciences; Frequency ranges; Geophysics/Geodesy; Microwave radiation; Microwaves; Observatories; Radiation sources; Radio telescopes; Solar eclipses; Solar limb; Sun; Telescopes; Water vapor; Wavelengths
• ISSN: 0016-7932; 1555-645X; 0016-7940
• DOI: 10.1134/S0016793223070125

The solar eclipse on October 25, 2022, is the ninth case of observations of solar eclipses using the fully rotatable RT-32 and RT-13 radio telescopes of the Institute of Applied Astronomy, Russian Academy of Sciences located at the Svetloye observatory in the Leningrad Region and Zelenchukskaya observatory in the North Caucasus. This eclipse is also the second case of observation using the WVR-4 water vapor radiometer as a full-fledged research tool for observing the Sun. Unlike the previous two eclipses in 2020 and 2021, when the Sun was at a deep minimum, the activity of the Sun in 2022 increased significantly, which made it possible to return to the traditional task of eclipse observations, i.e., the study of the fine spatial structure of various active solar formations, which should include the distribution of radio brightness near the solar limb. Observations on RT-13 and RT-32 have been performed at 1.0 cm, 3.5, 6.2, and 13 cm wavelengths with circular polarization analysis, and on WVR-4 at wavelengths of 0.96 cm and 1.45 cm in intensity. Individual details of the structure of microwave radiation sources have been identified by comparison with observations of the Sun in other frequency ranges. We have studied two morphologically different active regions (the region with a large NOAA 13 131 spot and an extensive spotless bipolar region) and the regions of contacts I and IV. The pre-processing of observations allowed us to obtain a quasi-two-dimensional distribution of the radio brightness of the NOAA 13 131 active region located close to the limb. The nature of the distribution changes significantly with the wavelength. A small-scale image structure associated with radiogranulation has been identified within the spotless active region (plage). The observations of contacts confirmed the previously found small value of the radio radius corresponding to a quasi-quiet atmosphere. We measured the brightness temperature of the Sun averaged over the disk in the range of the water vapor line (1.35 cm), which coincides within the error with observations of the eclipse of 2021.