Solar radio events and geomagnetic storms

On the basis of a 24-hr patrol of solar radio noise established since the beginning of the International Geophysical Year, an identification is attempted of those solar flares which, on account of their associated radio responses, most probably were the cause of a geomagnetic storm. The cases for which we think the identification to be reliable are listed. It has appeared that great integrated intensity of the radio outburst at centimeter, decimeter and meter wavelengths is the primary criterion for identifying the solar flares responsible. Most of these giant radio outbursts, to which we assigned the “radio importance” figure 3 +, belong to the so-called type IV. Only a minor fraction of these events were accompanied by slow-drift bursts of type II. Of the importance 3 + radio outbursts about 60 per cent are clearly associated with the subsequent sudden commencement of a geomagnetic storm. Conversely, about 50 per cent of the sudden commencements of a storm can be related to an important radio event. Some reasons, why in a particular case the storm-outburst association may fail to exist, are mentioned.