Propagation of type iii bursts emission in the solar corona. 1. Time profile

Abstract

Propagation of electromagnetic (EM) waves in the solar corona plasma from the generation point to the observer is investigated using the generally accepted plasma generation theory of the type III bursts. In particular we focus on the growth of the EM wave group velocity with the change of plasma density with distance from the Sun. An analytical expression for the group velocity of EM waves is obtained as a function of coordinates of the generation point and the distance from this latter. Group delays based on the analytic group velocity are calculated for two models of the corona. Taking into account spatial size of the electron beam yielded the EM radiation profile. We also consider the electron beams with fine structure and show that the EM radiation profile from such a beam is similar to the observed profiles of the type III bursts with fine structure. Finally, a spherical beam with monotonically increasing radius is considered, the dynamic spectrum and the type III bursts duration obtained over a wide frequency range.