The Solar Radius at 37 GHz Through Cycles 22 to 24

Selhorst C.L.; Kallunki J.; Gimenez de Castro C.G.; Valio A.; Costa J.E.R.

The Solar Radius at 37 GHz Through Cycles 22 to 24

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Artigo

Date

2019

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Solar Physics

item.page.citationsscopus

5

Authors

Selhorst C.L.
Kallunki J.
Gimenez de Castro C.G.
Valio A.
Costa J.E.R.

Abstract

© 2019, Springer Nature B.V.To better understand the influence of the activity cycle on the solar atmosphere, we report the time variation of the radius observed at 37 GHz (λ= 8.1 mm ) obtained by the Metsähovi Radio Observatory (MRO) through Solar Cycles 22 to 24 (1989 – 2015). Almost 5800 maps were analyzed, however, due to instrumental setup changes the dataset showed four distinct behaviors, which required a normalization process to allow for the whole interval analysis. When the whole period was considered, the results showed a positive correlation index of 0.17 between the monthly means of the solar radius at 37 GHz and solar flux obtained at 10.7 cm (F10.7). This correlation index increased to 0.44, when only the data obtained during the last period without instrumental changes were considered (1999 – 2015). The solar radius correlation with the solar cycle agrees with the previous results obtained at mm/cm wavelengths (17 and 48 GHz), nevertheless, this result is the opposite of that reported at submillimeter wavelengths (212 and 405 GHz).