A Solar Noise Outburst at 600 Mc./s. and 1,200 Mc./s

Abstract

SIMULTANEOUS records of solar radiation at 200 Mc./s., 600 Mc./s. and 1,200 Mc./s. have been made at this laboratory for approximately two hours per day since August 18, 1947. In general, the 200 Mc./s. radiation is similar in character to that described by McCready, Pawsey and Payne-Scott¹, showing a considerable number of short bursts and an increase in general level as some sun. spots cross the meridian. The 600 and 1,200 Mc./s records, on the other hand, show almost a complete absence of bursts, the level remaining fairly constant for any one day. The radiation received when the sun is almost free from sunspots corresponds to a solar black-body temperature of 0·5 million degrees Kelvin at 600 Mc./s. and 0·1 million degrees Kelvin at 1,200 Mc./s. and is almost certainly thermal in origin. As sunspots appear, the temperatures rise gradually and show close correlation with sunspot area. The maximum steady levels recorded to date are 1·0 million degrees at 600 Mc./s. and 0·2 million degrees at 1,200 Mc./s. The absence of rapid changes in level suggests that the radiation is still thermal in character, and it is thought that the increase is due to the magnetic field of the sunspots raising parts of the effective radiating shells into the corona², which is at a temperature of at least 1 million degrees.