Observations and interpretation of the slowly varying component of solar radio emission at decameter wavelengths

Abstract

It is shown that the detection of the slowly varying component of solar radio emission at decameter wavelengths during extremely quiet periods is possible. Such observations are presented for the case of emissions at 34.5 MHz during the periods of July-December 1979 and February-March 1980, with half power beam widths of 26/40 arcmin in the east-west and north-south directions, respectively. The measured brightness temperatures are found to vary within the limits of 300,000 to 1,500,000 K. The average half power width of the brightness temperature distribution of the sun is about three solar radii. It is shown that thermal emission from the dense coronal regions can account for the observed brightness temperatures and half power widths.