Statistical Survey of Type III Radio Bursts at Long Wavelengths Observed by the Solar TErrestrial RElations Observatory (STEREO)/Waves Instruments: Goniopolarimetric Properties and Radio Source Locations

TL;DR

This study provides a comprehensive statistical analysis of Type III radio bursts observed by STEREO, focusing on their goniopolarimetric properties and source locations, revealing extended source sizes and propagation characteristics in the interplanetary medium.

Contribution

It offers new insights into the source sizes, propagation, and scattering effects of Type III radio bursts at long wavelengths using STEREO data.

Findings

Source size $ ightarrow$ extends to about 60° at low frequencies

Source positions suggest propagation mainly in the ecliptic plane

Scattering significantly influences the observed radio source patterns

Abstract

We have performed statistical analysis of a large number of Type III radio bursts observed by STEREO between May 2007 and February 2013. Only intense, simple, and isolated cases have been included in our data set. We have focused on the goniopolarimetric (GP, also referred to as direction-finding) properties at frequencies between $125$ kHz and $2$ MHz. The apparent source size $\gamma$ is very extended ($\approx60^\circ$) for the lowest analyzed frequencies. Observed apparent source sizes $\gamma$ expand linearly with a radial distance from the Sun at frequencies below $1$ MHz. We have shown that Type III radio bursts statistically propagate in the ecliptic plane. Calculated positions of radio sources suggest that scattering of the primary beam pattern plays an important role in the propagation of Type III radio bursts in the IP medium.