Nature of Solar Radio Burst Spectra in Frequency Band 0.245-35 GHz

Abstract

A total of 132 solar radio burst spectra in the frequency band 0.245-35 GHz have been classified into 15 distinct types according to the nature of variation of emission intensity with the observed frequencies. Of these 15 types. IU-IU, IU-1, D-IU, D-I and U-IU occur most. They generally have the most pronounced peaks at 0.245-0.606 GHz and the less pronounced peaks at around 8.8 GHz. The mean spectral indices In the ranges of frequencies 0.245-0.606,1.415-2.695 and 4.995-15.4 GHz are 2.7, 1.3 and 1.0 respectively. In the decimetre-wave region the bursts having U-shaped spectra correlate well with type II metre-wave bursts and proton events. and the bursts having LS-shaped spectra with type III bursts. In the centimetre-wave region. IF-type spectra are associated With type III bursts and proton events and the D-type ones with type II bursts. The spectral shapes have been interpreted on recalling the existing knowledge of different types of emission and absorption mechanisms known 10 take place in the solar atmosphere.