Origin of solar type IV meter-wave storms

Abstract

The features of cyclotron radiation from electrons gyrating in the possible source regions of both "moving" and "stationary" solar type IV meter-wave storms are investigated. Assuming some models of spot magnetic field configuration and electron density distribution in the possible source regions, it is found that the majority of the important observed characteristics of type IV meter-wave storms can be well accounted for by the cyclotron mechanism. If we specify the magnetoactive plasma of the possible source region by the quantity A = fP2/fH2 (where fP = electron plasma frequency and fH = electron gyrofrequency), both the solar type I noise storm (Fung and Yip 1966a, b) and the second phase of type IV meter-wave storm are considered to be generated by cyclotron radiation from electrons in the o-mode, but in ambient magnetoactive plasmas of slightly different values of A. From our present investigation, cyclotron radiation in the x-mode from electrons trapped in "frozen-in" magnetic fields in a source region where A ≈ 0.1 can be applied to explain the main features of the type IV meter-wave first phase emission.