Absorption bursts in the radio emission from the sun at decameter wavelengths

Abstract

Some characteristics of sudden decreases in the observed radio emission from the sun at decameter wavelengths are presented, and possible interpretations are discussed. These 'absorption bursts' occurred during periods of steady continuum emission and also during long duration emission bursts. The steady level of the continuum corresponded to about 10 to 15 solar flux units. The intensity of the long duration emission bursts varied over a range of 10 to 300 SFU. The most common type of burst was one in which the fall in intensity and subsequent rise are smooth and structureless. Other types of bursts were characterized by their split time profiles or by their long duration. These sudden reductions may be due to quenching of the loss cone instability by the injection of new electrons, or to the absence of conditions required for conversion of the Langmuir waves into electromagnetic waves by induced scattering.