Source Regions of the Type II Radio Burst Observed During a CME-CME Interaction on 2013 May 22

TL;DR

This study uses direction finding analysis of radio observations to identify the source regions of a type II radio burst during a CME-CME interaction, revealing spatial shifts and confirming the interaction region as the source.

Contribution

It provides the first detailed localization of type II radio burst sources during CME interactions using triangulation and multi-spacecraft data.

Findings

Radio sources near the line connecting Sun and STEREO-A

Source locations shift during CME interaction

CME-CME interaction region is the source of type II emission

Abstract

We report on our study of radio source regions during the type II radio burst on 2013 May 22 based on direction finding (DF) analysis of the Wind/WAVES and STEREO/WAVES (SWAVES) radio observations at decameter-hectometric (DH) wavelengths. The type II emission showed an enhancement that coincided with interaction of two coronal mass ejections (CMEs) launched in sequence along closely spaced trajectories. The triangulation of the SWAVES source directions posited the ecliptic projections of the radio sources near the line connecting the Sun and the STEREO-A spacecraft. The WAVES and SWAVES source directions revealed shifts in the latitude of the radio source indicating that the spatial location of the dominant source of the type II emission varies during the CME-CME interaction. The WAVES source directions close to 1 MHz frequencies matched the location of the leading edge of the primary CME seen in the images of the LASCO/C3 coronagraph. This correspondence of spatial locations at both wavelengths confirms that the CME-CME interaction region is the source of the type II enhancement. Comparison of radio and white-light observations also showed that at lower frequencies scattering significantly affects radio wave propagation.