Low-level decimetric (1.6 GHz) solar burst activity

Observations of solar bursts at 1.6 GHz were carried out in the month of July 1985 for about two weeks. Five intervals of solar burst activity, each one lasting for a couple of minutes, were observed. Predominantly, two classes of fast bursts were observed: viz: spike and blips. However, some of these bursts were two orders of magnitude less intense than those reported earlier.Low-level blips have typical duration 350 ms, excitation time 200 ± 25 ms, decay time 130 ± 25 ms and a low degree of circular polarization of about 15%. Detailed investigations of decay times of the blips have been carried out in terms of collisional damping and Landau damping. Observed decay times of the blips seem to favour the hypothesis of collisional damping. This investigation suggests that blips probably originate at second harmonic by beam plasma interaction as that of metric type III bursts. Also, low-level ms-spikes with the half power duration in the range of 5 to 20 ms suggest that source sizes be smaller than 50 km if the process of emission is electron-cyclotron maser.Proceedings of the Second CESRA Workshop on Particle Acceleration and Trapping in Solar Flares, held at Aubigny-sur-Nère (France), 23–26 June, 1986.