2800 megacycle per second radiation associated with type II and type IV solar radio bursts and the relation with other phenomena

Emission at 2800 Mc/s (λ = 10.7 cm) has been examined for 164 solar flare events in 1957–1961 that displayed type II and/or type IV emission at meter wavelengths. Characteristics of the centimeter bursts are presented and discussed in relation to the meter bursts, flares, the magnetic class of the associated sunspots, ionospheric disturbances (SWF), and geomagnetic and solar proton (PCA) effects. No centimeter bursts were detected for 13% of the events; bursts with an impulsive profile were observed for 82% of the events. Of the impulsive bursts, 74% reached maximum quickly, displaying a simple, narrow burst profile (average half-width 1.8 minutes); the rest had complex profiles containing a predominant broad component (average half-width 17 minutes). The narrow profile bursts are considered to be M type, and the broad profile bursts to evidence type IVμ emission. The majority of the narrow profile centimeter bursts corresponded to events in which only a type II burst was observed at the meter wavelengths. When type IV bursts were observed at the meter wavelengths, narrow profile centimeter bursts were seen in 43% of the cases and broad profile bursts in 57%. A strong association with magnetically complex sunspots, flares of importance ≥2+, SWF of importance ≥3−, geomagnetic storms, and PCA was found for only those events in which the centimeter burst had a broad profile. It is concluded that the peak intensity and the half-width of the burst profile at 2800 Mc/s enable solar events with a significant association with geomagnetic and PCA activity to be recognized.