Using radio triangulation to understand the origin of two subsequent type II radio bursts

¹ SIDC, Royal Observatory of Belgium, Brussels, Belgium
e-mail: immanuel.jebaraj@oma.be
² Centre for mathematical Plasma Astrophysics, KU Leuven, Leuven, Belgium
³ Skolkovo Institute of Science and Technology, Moscow, Russia
⁴ University of Helsinki, Helsinki, Finland
⁵ Institute of Physics, University of Graz, Graz, Austria
⁶ Kanzelhöhe Observatory for Solar and Environmental Research, University of Graz, Graz, Austria
⁷ Goddard Planetary Heliophysics Institute, University of Maryland, Baltimore County, Baltimore, MD 21250, USA
⁸ Heliospheric Physics Laboratory, Heliophysics Division, NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA
⁹ Institute of Physics, University of Maria Curie-Skłodowska, 20-031 Lublin, Poland

Received: 6 December 2019
Accepted: 7 May 2020

Abstract

Context. Eruptive events such as coronal mass ejections (CMEs) and flares accelerate particles and generate shock waves which can arrive at Earth and can disturb the magnetosphere. Understanding the association between CMEs and CME-driven shocks is therefore highly important for space weather studies.

Aims. We present a study of the CME/flare event associated with two type II bursts observed on September 27, 2012. The aim of the study is to understand the relationship between the observed CME and the two distinct shock wave signatures.

Methods. The multiwavelength study of the eruptive event (CME/flare) was complemented with radio triangulation of the associated radio emission and modelling of the CME and the shock wave employing MHD simulations.

Results. We found that, although temporal association between the type II bursts and the CME is good, the low-frequency type II (LF-type II) burst occurs significantly higher in the corona than the CME and its relationship to the CME is not straightforward. The analysis of the EIT wave (coronal bright front) shows the fastest wave component to be in the southeast quadrant of the Sun. This is also the quadrant in which the source positions of the LF-type II were found to be located, probably resulting from the interaction between the shock wave and a streamer.

Conclusions. The relationship between the CME/flare event and the shock wave signatures is discussed using the temporal association, as well as the spatial information of the radio emission. Further, we discuss the importance and possible effects of the frequently non-radial propagation of the shock wave.