A group of solar microwave type-III bursts on 1998 April 15

We describe in detail a group of microwave type-III bursts observed on 1998 April 15 by the 2.6–3.8 GHz solar radio spectrometer of Beijing Astronomical Observatory. The bursts are characterised by broad bandwidths (> 100MHz), short durations (< 100ms), very high degrees of polarization (∼ 100%), positive rates of frequency drifts (> 1 GHz/s) and fast pulsations (with periods of about 100 ms). Their time profiles are also analyzed. According to these characteristics, we suggest that they originate from plasma fundamental wave emission.