A Scenario for the Fine Structures of Solar Type IIIb Radio Bursts Based on the Electron Cyclotron Maser Emission

TL;DR

This paper proposes a scenario based on electron cyclotron maser emission to explain the fine structures of solar Type IIIb radio bursts, focusing on modulation effects by ultra low frequency waves and addressing key observational features.

Contribution

It introduces a new physical mechanism involving plasma and gyro-frequency modulation to explain the fine structures and specific characteristics of Type IIIb solar radio bursts.

Findings

Explains the intermittent emission elements in Type IIIb bursts.

Accounts for split pair and triple stria features.

Clarifies why certain fundamental-harmonic emission pairs are rare.

Abstract

A scenario based on the electron cyclotron maser emission is proposed for the fine structures of solar radio emission in the present discussion. It is suggested that under certain conditions modulation of the ratio between the plasma frequency and electron gyro-frequency by ultra low frequency waves, which is a key parameter for excitation of the electron cyclotron maser instability, may lead to the intermittent emission of radio waves. As an example, the explanation of the observed fine-structure components in the solar type IIIb burst is discussed in detail. Three primary issues of the type IIIb bursts are addressed: 1) what is the physical mechanism that results in the intermittent emission elements that form a chain in the dynamic spectrum of type IIIb bursts, 2) what causes the split pair (or double stria) and the triple stria, 3) why in the events of fundamental-harmonic pair emission there is only IIIb-III, but IIIb-IIIb or III-IIIb cases are very rarely observed.