Spectra of Solar Radio Type IV Bursts

Abstract

Abstract Dynamic spectra of intense outbursts with long duration are studied in a frequency range of 9400 Mc to 67 Mc by using single frequency records. There occur at least two distinctive groups of outbursts in a course of such an outburst. One is long-duration outburst on centimeter-waves (group A) and the other is believed to be type IV burst on meter-waves (group B). These groups occur with a clear gap in frequency range or are mixed in some frequency range accompanying another group on decimeter-waves (group A – B). The type IV bursts on meter.waves are frequently followed after an intermission of 30~60 minutes by similar but longer and weaker radiations (group C). The bandwidth of individual groups except group A is rather narrow so that the energy of electrons emitting synchrotron radiation is estimated assuming quasi-circular orbits to be of the order of 105 eV. It is shown that group A is not high frequency component of group B, but groups A and B are radiated from two separate sources with different physical properties. It is suggested to call group A as “centimeter-wave type IV”, group A–B as “decimeter-wave type IV”, group B as “meter-wave type IV” and group C as “meter-wave post-type IV”.