Exponential Decay and Exciter Profile of Fast Pulses in Type IV Events

Abstract

Some fast bursts occurring at 237 MHz during type IV events in association with sawtooth pulsations have been studied. These bursts, when occurring sufficiently isolated from the adjacent pulsating activity, appear to have an exponential decay phase similar to that of fast type III bursts.

A computational procedure, based on Fourier transform techniques, has been applied; it allows the computation, for every observed point in the time profile, of the corresponding value for the logarithmic derivative and for the exciter function. The results so far obtained show that the time decay value is of the same order observed for normal type Ill’s. As the bursts studied appear clearly not to be type Ill’s (mainly for their total polarization), but isolated components of pulsation groups, this result may be an interesting indicator of the emission mechanism (plasma waves excitation and its abrupt stop) involved in type IV decimetric pulsations.

Proceedings of the Workshop on Radio Continua during Solar Flares, held at Duino (Trieste), Italy, 27–31 May, 1985.