A decimetric (1600 ± 100 MHz), high-sensitivity digital spectroscope has been put into regular operation at São José dos Campos, Brazil, since 1991 March. The dynamic spectra are recorded on 35 mm film while 20 frequencies each separated by 10 MHz are digitized with time resolution of 100 ms. So far, about 350 groups of solar bursts have been observed by this system. These have been classified as microwave type and decimetric reverse slope (RS) type III bursts. Here, we report statistical investigations of the properties of the 44 moderately strong groups of decimetric type III-RS bursts. The average total duration of these bursts is ~0.7 s, the drift rate varied between ~400 and 3000 MHz s−1 , and average decay time is ~120 ms. These observed drifts and timescales suggest that decimetric type III-RS bursts are generated by beam plasma interaction at second harmonic in the inhomogeneous chromosphere, and that the acceleration region is located at a density level of ≤109 cm−3 .
Subject heading: Sun: radio radiation