Jebaraj, Immanuel; ; Poedts, Stefaan; ; Krupar, Vratislav; ; Magdalenic, Jasmina

Talk presented at 43rd COSPAR Scientific Assembly, Sydney, Australia on 2021-01-31

Abstract: Although solar radio bursts are studied for well over 60 years, and there are still a number of open questions on their generation and emission processes. It is generally accepted that majority of solar radio bursts observed in the corona is due to the coherent plasma emission mechanism, and a substantial amount of work has been done to support this idea. The study of fine structures of solar radio bursts can therefore help us to understand plasma processes in the corona and interplanetary space. While most of the works done in this respect are using older observational facilities, new and advanced ground-based radio imaging spectroscopic techniques (using e.g. LOFAR, MWA, etc.,) and space-based observations (Wind/WAVES, STEREO/WAVES A & B, PSP, and SolO in the future) provide a unique opportunity to identify, and study fine structures observed in the low corona and interplanetary space. Although, extensive studies of fine structures have been performed for the metric radio bursts, not much work was devoted to study the fine structures of interplanetary radio emission. Radio signatures of solar dynamic phenomena observed in interplanetary space are mostly confined to two different types, type II bursts (due to propagating MHD shock waves), and type III bursts (suprathermal electron beams propagating along open and quasi-open magnetic field lines). In this study, three types of fine structures of interplanetary radio bursts are presented. The striae-like fine structures within type IIIb bursts, continuum-like emission patches, and drifting narrowband structures within type II radio bursts. Since space-based radio observations are limited to dynamic spectra, we use the novel radio triangulation technique employing direction finding measurements from spacecraft observations (Wind/WAVES, STEREO/WAVES A & B) to estimate 3D positions of the radio emission sources. Results of the study show that locating the radio sources of fine structures can help us understand their generation mechanism and the plasma conditions necessary for generating them. We discuss the possible relationship between the fine structures, the broadband emission they are part of, and the associated solar eruptive events.