Spectral characteristics of medium-sized solar radio events

Peak intensities at different frequencies, as reported by several solar radio patrol stations, are used to study the spectrum at the time of maximum intensity of medium-sized solar radio events that cover both the centimetric and metric frequency bands. Two types of spectrum can be distinguished: a V-type of spectrum, where the straight lines, that can be drawn to represent the centimetric and the metric branches, meet each other at a frequency somewhere in the decimetric frequency range and a Jump-type of spectrum, where a discontinuity occurs somewhere in the low-frequency part of the decimetric spectrum. The aspect of the radio response at 600 MHz may have a character which is more centrimetric or more metric. Its character tends to correspond to the spectral branch (metric or centimetric) to which, according to the spectrum, the 600 MHz burst belongs. It is concluded that the centimetric and the metric branch of a cm/m-event are largely independent of each other. It is suggested that a Jump-type of spectrum occurs if some condition relating to the coronal magnetic field is fulfilled.