The quiet and slowly varying components of 9.1 cm radio emission during the solar minimum

Radio emission from the sun at a wavelength of 9.1 cm has been studied during the quiet sun years, 1964–65, using the Stanford spectroheliograph. A map of the quiet sun has been prepared and compared with a map produced using the same instrument in 1960. On the basis of ray tracing results the differences in the two maps can be explained by a decrease in the electron density by a factor of 1.4 at the equator and 1.1 at the poles.The slowly varying component of emission can be attributed to electron density enhancements by a factor of 2 to 5 over regions with dimension 2 to 6 arc. Changes of flux and width of these regions with longitude on the sun agree with the results of ray tracing using a very simple model for the regions. The detection of sunspot groups on the far side of the sun by measuring increased 9.1 cm emission at the limbs is shown to be possible.