A Study of Long-Term Solar Activity at 37 GHz

In this paper we investigate the solar activity at the radio frequency (37 GHz) using an extensive data series (solar radio maps) from the Metsahovi Radio Observatory. This paper aims to present this unique solar radio map collection to the public knowledge. The data set covers the years from 1978 to 2011 (solar cycles 21-24). We investigate the long-term solar activity on the ground of the distribution of solar radio brightenings and the differential rotation of the Sun.