The features of microwave solar radiation observed in the stage of formation and initial propagation of geoeffective coronal mass ejections

We consider sporadic radio emission which precedes recording of geoeffective coronal mass ejections, using the data of broadband patrol observations of the Sun in the centimeter-, decimeter-, and meter-wave ranges in some periods of the XXIst–XXIIIrd solar-activity cycles. The total amount of used information instruments covers 339 events and includes the data from the radioastronomical facility “Zimenki” of the Radiophysical Research Institute and from the world solar service in the radio-frequency range, as well as the catalogs of coronal mass ejections recorded by the SMM and SOHO/LASCO instruments. On the basis of statistical analysis, we reveal the regular features in the characteristics of sporadic microwave emissions observed in the twohour interval before the coronagraph detection of geoeffective coronal mass ejections, which were defined as radio precursors of such coronal mass ejections. The revealed features in the characteristics of the radio precursors of geoeffective coronal mass ejections involve the presence of the broadband centimeter–decimeter radio emission for over 10 min in the stage preceding the coronal ejection redetection by coronagraphs. Such radio precursors are shown to precede loop-like halo, and partial halo coronal mass ejections, which have maximum potential geoeffectiveness. The radio-emission behavior, which does not meet the established regular features, is also analyzed.