Identifying 8 mm Radio Brightenings During the Solar Activity Minimum

Juha Kallunki*, Merja Tornikoski, Irene Björklund

*Tämän työn vastaava kirjoittaja

Tutkimustuotos: LehtiartikkeliArticleScientificvertaisarvioitu

102 Lataukset (Pure)

Abstrakti

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.

AlkuperäiskieliEnglanti
Artikkeli105
Sivumäärä11
JulkaisuSolar Physics
Vuosikerta295
Numero7
DOI - pysyväislinkit
TilaJulkaistu - 1 heinäkuuta 2020
OKM-julkaisutyyppiA1 Julkaistu artikkeli, soviteltu

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