Some new observing features of a solar radio spectral event on August 25, 1999

A broad band solar radio type III burst was observed on August 25,1999 at P urple Mountain Observatory with waveband of 4.5-7.6 GHz. It was also observ ed at Beijing Astronomical Observatory with waveband of 5.2-7.6 GHz. Theref ore, it is the first common spectral event observed in China. The type III bursts are gathered into more than 10 groups and drift in opposite directio ns, but the reverse drifting prevails. The largest bandwidth of type III bu rst reaches greater than or equal to3 GHz and may be the broadest bandwidth of the reverse type III burst ever observed up to the present. Some new ob serving characteristics of fine structures are found, for example, fiber-li ke, V-shaped and neck-ringlike structures. Especially, the neck-ring-like s tructure is probably first discovered in cm waveband and may be the evidenc e of twisted rope of magnetic lines.