The time-latitude distribution of solar flares accompanied by type IV radio bursts during the period 1956 to 1969

Abstract

A list of nearly 350 flares accompanied by type IV radio bursts by Krüger et al. (1971), which covers a period of 14 yr (1956–1969), was expanded to include all PCA and solar cosmic ray events during this entire period. This list, which includes practically all of the most energetic events during the maxima of two consecutive solar cycles, was used to investigate the latitudinal distribution of the above-mentioned flares, as well as of all PCA events, solar cosmic ray events and plage regions associated with them.

Histograms of these occurences show clearly the appearance of two peaks in both solar maxima, which confirm the observations of Gnevyshev (1967). Latitudinal analysis of these histograms shows that in cycle 20 the two peaks are independent and their relative strength varies strongly with latitude. In cycle 19, however, this effect is not clearly evident, possibly because of the extremely high level of activity during this cycle. In both cycles, the second maximum shows the highest concentration of the most energetic events.