Solar microwave combined type-III bursts

Abstract

We call a “microwave combined type III burst” when there is a microwave common type III burst at the low frequency end and a simultaneous microwave continuous type U burst at the high frequency end. The latter is the result of further evolution of single microwave type U bursts in one and the same magnetic ring, and, as such, is still a subtype of type III bursts. Hence the whole combined type III burst is also a subtype of type III bursts. The source of radiation of the microwave combined type III burst (i.e. high-energy electron beams) comes from one and the same region of acceleration. But in its interaction with magnetic rings in low coronal regions an electron beam is divided into two beams, one of captured electrons and one of escaping electrons. These beams have different trajectories of motion and give rise to simultaneous continuous type III burst at the high frequency end and common type III burst at the low frequency end. The formation of the combined burst is closely related to the structure of magnetic rings in the low coronal regions, so it is peculiar to the microwave range.