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A partial solar eclipse occurred on 25 October 2022, in the central and northern parts of Europe. The partial solar eclipse was observed at Aalto University Metsähovi Radio Observatory, Finland at the radio wavelength of 8 mm (37 GHz). In Finland, the magnitude of the partial solar eclipse was 62.7 %. Solar radio maps at the time cadence of about 9 minutes were observed over the whole eclipse. The solar eclipse observations could be used for instrument calibration purposes. This paper investigates the solar brightness temperature, the limb brightening effect, the height of the chromosphere and the location of radio brightening using the aforementioned partial solar eclipse observations. We got the confirmation that our earlier results are consistent, e.g., the solar brightness temperature matches with 8100 K ± 300 K. It was also possible to detect limb brightening effect. However, the prevailing solar activity might have distorted the final conclusions. The Moon should operate as a focusing element and the location of radio brightenings could be defined more carefully than in the normal conditions. We investigated this feature. Our results are in some parts unexpected and need further investigations. [ABSTRACT FROM AUTHOR]

Nowadays there is increasing interest in narrowing coronal areas with reduced brightness temperatures (LTR – Low Temperature Regions) associated with local open magnetic fields (S-web, "coronal partings", "dark coronal corridors") as one of the eventual sources of slow solar wind. Ventspils International Radio Astronomy Centre (VIRAC) performs routine spectral polarimetric observations of the Sun with RT-32 radio telescope equipped with the multi-channel (16 frequency channels) spectral polarimeter for the wave length range of 3.2–4.7 cm (6.3–9.3 GHz) and both circular polarizations simultaneously. The analysis of relevant tasks of clear and reliable observations and detections of LTR shows the necessity to improve noise parameters, dynamic range and stability of the actual solar spectral polarimeter and to expand its wavelength range. Taking into account these requirements, the low noise and thermally stabilized solar spectral polarimeter was developed. The new multi-channel spectral polarimeter is expected to observe right and left circular polarization of the solar emission in the wavelength range of 2.1–7.5 cm (4.1–14.3 GHz) divided into 12 frequency bands. The dynamic range was expanded to >36 db and the signal/noise ratio (referred to as quiet Sun brightness temperatures) was enhanced to > 22–24 db. The paper deals with some test observations of the newly developed solar spectral polar-imeter and its feature analysis. Some eventual problems of solar physics which could be solved with the spectral polarimeter are also discussed. [ABSTRACT FROM AUTHOR]