Motion of high latitude solar microwave sources and comparison with polar prominences

Solar microwave sources at high solar latitudes have been observed with a 14 m radio telescope at the Metsahovi Radio Research Station in Finland. Several periods for observations were organized in 1986–1989 in order to detect sources close to the north and south pole of the Sun. Measurements at 22 and 37 GHz (wavelengths 14 and 8 mm respectively) have revealed the existence of high temperature and low temperature regions (relative to the quiet Sun level) at latitudes 50–80 degrees. The motions of these regions have been studied and compared with optical measurements of polar prominences. The temperature enhancement at 37 GHz is typically 100–400 K above the quiet Sun level (7800 K) at that frequency. Although in most cases temperature depression in a low temperature area amounts 50–300 K, at 37 GHz, the temperature drop in the low temperature area which was observed in July 1982 was as low as 900 K. The results of the radio measurements of the Sun at 22 and 37 GHz on high solar latitudes imply that high temperature areas correspond to polar faculae while low temperature areas correspond to polar prominences. The principal cause of the observed lower temperature area is the absorbtion by the filament.