STATISTICAL STUDY OF MOVING TYPE-IV BURSTS BASED ON CULGOORA RADIOHELIOGRAPH OBSERVATIONS

Thirty-one moving type IV (IV(M)) bursts recorded with the Culgoora radioheliograph are examined to deduce their characteristic features, such as spatial distribution, projected velocity, etc., and their relation to other phenomena. The distribution of the projected velocity suggests that less than 15% of the total IV(M) bursts have fast velocities (>1000 km s-1), almost equal to MHD shock velocity, and that the remaining IV(M) bursts have slower velocities (∼400 km s-1) and are probably not associated with MHD shock waves. Most of the slow IV(M) bursts (and ≳70% of the total IV(M) bursts) are of an isolated plasmoid type. Even if they are associated with minor Hα flares, IV(M) bursts of the isolated-plasmoid type have ∼1031 ergs in the form of magnetic energy. They are in many cases closely associated with extended flare-continuum sources; this seems plausible if the flare continuum is interpreted as an interaction of a plasmoid with a large-scale magnetic arch. The association of IV(M) bursts with energetic proton events seems to be poor - contrary to expectation. © 1979 D. Reidel Publishing Company.