Decameter type IV bursts associated with coronal transients

Abstract

The characteristics of four moving type IV bursts, observed with the 65-20 MHz sweptfrequency interferometer of the Clark Lake Radio Observatory are discussed. All four bursts were associated with depletions in the electron content of the white light corona. Characteristics of the bursts are not unique, i.e. they differ in source size, structure, duration and their association with other radio bursts. Following Smerd and Dulk (1971) we believe that a shock wave, moving out from the flare site is responsible for the expansion of a magnetic arch or the ejection of a plasmoid which is observed as the usual type IV burst. Behind the shock wave, the compressed coronal gas moves outward, and as it expands it causes a depletion of electrons in the inner corona. After the passage of the shock wave, sometimes the coronal magnetic field structure is restored to its initial situation, as evidenced by the observation of homologous transients.