Modulation of radio source radiation at a frequency of 37 GHz by long-period oscillations of a nearby sunspot

Smirnova, V. V.; Соловьев, А. А.; Riehokainen, A.; Kallunki, J.

doi:10.1134/s001679321507021x

Cited by 3 publications

(1 citation statement)

References 9 publications

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“…The magnetogram maps show the solar magnetic field strength in the photosphere. The location of the magnetic field in the photosphere matches with the locations of the radio brightening [10], [11]. In Fig.…”

Section: Location Of the Active Region (Radio Brightening)supporting

confidence: 60%

Using Partial Solar Eclipse for the 14-Metre Radio Telescope Calibration

Kallunki

2023

Latvian Journal of Physics and Technical Sciences

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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.

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Section: Location Of the Active Region (Radio Brightening)supporting

confidence: 60%

Using Partial Solar Eclipse for the 14-Metre Radio Telescope Calibration

Kallunki

2023

Latvian Journal of Physics and Technical Sciences

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Identifying 8 mm Radio Brightenings During the Solar Activity Minimum

2020

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Strong solar radio brightenings have been extensively studied in the past, and their correlation to the sunspots and active regions are already well known. But even when the Sun is ostensibly quiet, there is practically always some activity that can be detected in the radio domain. In this article we investigate these semi-active features at 8 mm using the radio telescope at Aalto University Metsähovi Radio Observatory. The observations were made between May and September 2019 when the solar activity was very low, and for our detailed study we chose dates when no active regions were identified on the solar surface by the National Oceanic and Atmospheric Administration. The brightness temperature of these radio regions during this quiescent period of solar activity is at maximum approximately 250 K above the quiet-Sun level. We compared our millimeter data with data taken in extreme ultraviolet, and we found that these weak radio brightenings are mostly related to coronal hole features and magnetic bright points. We also found that there are two different categories of bright points: those with and without flux tube structure. The formation of the weak radio brightenings is comparable to the stronger radio brightenings: the rising fluxes from the weak photospheric features can be detected as a radio source. Keywords Chromosphere, quiet • Solar cycle, observations 1. Introduction Even when the Sun is ostensibly quiet and there are no visible, classified active regions (ARs) on the solar disk, there is often some activity, such as coronal holes and magnetic bright points. Also solar radio observations practically always detect some activity. During B J. Kallunki

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