A Theory of Solar Type IV Emission on Centimetre and Decimetre Wavelengths

Abstract

Assuming models for electron density and magnetic field configuration in the lower solar active corona, it is proposed that type IV bursts on centimeter and decimetre wavelengths are the results of cyclotron radiation from helical electron streams. In order to explain the observed polarization features and spectral variabilities, the characteristics of cyclotron radiation from electron streams and the propagation of electromagnetic waves in the active corona are investigated. Adopting the current model for flare evolution, most of the properties of type IV bursts on centimetre and decimetre wavelengths are well interpreted by the present theory.