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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. [ABSTRACT FROM AUTHOR]

Measurements of the flux densities of the supernova remnant (SNR) G74.9+1.2 (CTB 87) at frequencies of 4840 and 8450 MHz were carried out with the RT-32 radio telescope of the Svetloye observatory of the Institute of Applied Astronomy, Russian Academy of Sciences (IAA RAS), in 2018–2019. The data contain signs of the presence of a source of a variable component in the radio emission on a time scale of a month or more. The flux densities of G74.9+1.2 over the time interval 1959.7–2010 are determined from published data, which allow the intensity of G74.9+1.2 to be compared with standard sources. All the data are presented in a single system based on the exact scale of "artificial moon" (AM) fluxes. A refined spectrum of SNR G74.9+1.2 was obtained. The totality of available data is approximated by two power-law sections with different spectral indices: at frequencies and at . The projections of two power-law sections intersect at a frequency MHz. The break in the radio spectrum of the source, considering its age (more than 4000 years), could form as a result of synchrotron losses. The increase in the steepness of the spectrum close to 0.5 above the frequency is an argument in favor of such an assumption. The totality of data obtained during measurements on the RT-32 and on the basis of published works allows us to state that the variable component in the G74.9+1.2 radio emission on all time scales is much less pronounced compared to younger PWNs. As a possible mechanism for the observed variability, a reconnection of the magnetic field lines in the pulsar magnetosphere is proposed. [ABSTRACT FROM AUTHOR]

The flux densities and current spectra of plerions and combined supernova remnants (SNRs): 3C58, 3C144, G11.2–0.3, G21.5–0.9, and 3C396 are determined on an artificial moon (AM) flux scale. The radio emission variability of the objects on different time scales is studied by multiple measurements using the RT-32 radio telescope at the Svetloe Observatory, Institute of Applied Astronomy, Russian Academy of Sciences and by mutual comparisons of the published measurement data, which have been brought to a common system using the AM flux scale. The radio emission from the SNRs displays both slow evolutionary variations and rapid ones, nonstationary in time. The rapid variability of the SNRs has features that are similar to those observed during solar flares. This fact may testify to the identity of the physical mechanisms underlying the rapid variability of the radio emission from plerions and from the Sun. Field line reconnections are considered as such a common mechanism. [ABSTRACT FROM AUTHOR]

The spectrum of G11.2-0.3 has been refined by bringing the published intensity measurements to the "artificial moon" flux scale, and the dynamics of its changes on different time scales from 0.4 to more than ~50 years has been investigated. An increase in the fluxes of radio emission of G11.2-0.3 for ≥30 years at 3 cm cm with a frequency dependence was found: the average rate of changes decreases proportionally to , and at frequencies GHz, the increase gave way to a decrease. Measurements with the RT-32 radio telescope of the Svetloe observatory (IAA RAS) in 2013–2019 showed a decrease in fluxes of G11.2-0.3 against the background of rapid nonstationary changes with an average rate of () %/year at a wavelength cm and ( %/year at cm. The stages of growth and decline of fluxes are separated by an epoch . The spectrum of G11.2-0.3 is the spectra sum of the shell and the plerion, with each of its parameters determined by the method developed for the 1972.5 epoch. The values of the spectral indices α1 of the shell and α2 of PWN are obtained: and . The dynamics of radio emission from the remnant reflects the scenario of interaction between the shock wave and CSM. Possible reasons for evolutionary and non-stationary changes are discussed. [ABSTRACT FROM AUTHOR]

Using the RT-32 radio telescope of the "Svetloe" IAA RAS observatory in 2017–2018, the flux density measurements of the combined (composite) supernova remnant (SNR) 3С396 (G39.2-0.3) at frequencies of 4840 and 8450 MHz are presented. The data obtained demonstrate source variability. Published data were used to determine the 3C396 flux density in 1962–2008 based on a comparison of the intensities of 3C396 and standard sources. To reduce all the data to a unified system, we used the "artificial moon" (AM) flux scale. A refined spectrum of SNR 3C396 was obtained, which is approximated as the sum of two power-law components with spectral indices α1 = 0.5 and α2 = 0.157. It is assumed that the components of the spectrum are due to emission from the shell and plerion, respectively. The plerion contribution to the SNR's total flux is estimated: at a wavelength λ = 21 cm, it is close to 30%. Earlier, the contribution estimate was based on X-ray data and did not exceed 4%. The above discrepancy is eliminated if there is a kink in the spectrum of the plerion, similarly to spectra 3C58 and G21.5-0.9. The data obtained during measurements with RT-32 and based on published works show changes in the source flux density on different time scales, from short time intervals (tmin < 0.5 years) or more. The localization and possible causes of detected variability are discussed. [ABSTRACT FROM AUTHOR]

We measured the instantaneous spectra of the supernova remnant 3C58 for the epochs: 2003.4, 2004.4, and 2013.2 with the RTF-32 radio telescope of the "Svetloe" IAA RAS observatory at four frequencies from 1550 to 8450 MHz. The spectra of 3C58 for the time intervals: 1963–1971, 1981–1998, and 2004–2010 were obtained from the published data allowing us to compare the intensity of 3C58 and standard sources. To reduce all the data to a unified system and build the spectra, we used the "artificial moon" flux scale. Comparison of the spectra according to the data obtained in 1963–2013 revealed non-stationary frequency-dependent variations of flux densities, as well as local deviations of the 3C58 spectra from the frequency power law. Possible causes of the detected anomalies are discussed. [ABSTRACT FROM AUTHOR]