Observations of the Spectrum of High-Intensity Solar Radiation at Metre Wavelengths. IV. Enhanced Radiation

Abstract

Observations are described of the spectrum of " enhanced radiation" from the Sun (i.e. the radio-frequency radiation which maintains a high but variable level for periods of hours' or days' duration) in the frequency range 70-130 Mc/s. This radiation is known to be received from the direction of sunspots and to show circular polarization. For the purpose of presenting results, two components are recognized, viz. a background continuum which varies gradually with time and frequency, and short-lived, narrow-band bursts (" storm bursts "). The behaviour of the two components, and the relation between them during periods of high level (" noise storms ") are described. A detailed analysis is given of the properties of recorded storm bursts. The distribution of recorded bursts with frequency was found to be markedly non- uniform, e.g. a pronounced minimum at 89 Mc/s. was present. The possibility that the background continuum is due to the resultant of a large number of bursts is discussed.