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Astron. Astrophys. 333, 741-745 (1998)

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Enhanced temperature regions in the polar zones of the Sun

A. Riehokainen 1, S. Urpo 2 and E. Valtaoja 1

1 Tuorla Observatory, FIN-21500 Piikkiö, Finland
2 Metsahovi Radio Research Station, FIN-02150 Kylmälä, Finland

Received 27 June 1997 / Accepted 9 January 1998


Some aspects of regions with enhanced temperature in the polar zones of the Sun are studied in this paper, using data from Metsähovi Radio Research station in Finland. In addition to low latitude sources, measurements at 36.8 GHz have also revealed the existence of apparently separate class of sources with enhanced temperatures at latitudes above 40 degrees. The motions of these regions have been used to determine the solar differential rotation rate at high latitudes. We also study both the spatial and the temporal distributions of the enhanced regions. The activity of the low latitude component follows the sunspot activity over a solar cycle. The high latitude component is of unknown origin, but our data indicates a possible connection between these regions and polar faculae.

Key words: Sun: radio radiation – rotation

Send offprint requests to: A. Riehokainen


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© European Southern Observatory (ESO) 1998

Online publication: April 20, 1998