Jebaraj, Immanuel.C; ; Kouloumvakos, Athanasios; ; Magdalenic, Jasmina; ; Rouillard, Alexis; ; Warmuth, Alexander; ; Mann, Gottfried; ; Krupar, Vratislav; ; Poedts, Stefaan; ; Vainio, Rami

Talk presented at AGU Fall meeting 2021 on 2021-12-16

Abstract: Type II radio bursts are generally observed in association with flare-generated or CME-driven (coronal mass ejection) shock waves. They are signatures of fast electron beams which are accelerated at the shock front. The exact shock and coronal conditions necessary for the production of the type II radio emission are still debated. The preferred location of the type II radio sources on the surface of the shock wave, can either be at regions close to the CME/shock leading edge or at the CME/shock flanks, or both, and has been a long-standing discussion. We address this question in a twofold study: In Kouloumvakos et al. (2021), we study a coronal shock wave associated with a multi-lane metric type II on 05 November 2014 and in Jebaraj et al. (2021), we study a shock wave associated with a flare/CME event and a complex radio event on September 27, 2012. In these studies, we employ a novel approach, combining shock wave modelling with radio techniques such as radio triangulation. Using, data from radio observatories and modern modeling techniques, we study the evolution of the shock waves in the low corona and in interplanetary space. First we reconstruct the shock wave in 3D space using multi-viewpoint observations of the solar corona and then we estimate the evolution of shock wave parameters in 3D using an MHD model of the background corona produced by the MAS (Magnetohydrodynamics Around a Sphere) model. Our results are based on a two-step analysis. We first analyze the global evolution of the wave parameters and then localize the areas which could be the source regions of radio emission. We study the temporal evolution of the upstream plasma characteristics and the shock wave parameters. We have visualized the complex relationship between the different shock wave parameters in a novel way by producing synthetic radio spectra. The conclusions of the two studies have been published in separate papers and suggest that the shock wave geometry and its relationship with the shock strength seem to play the most vital role in the generation of type II radio emission.