Multiple Sources of a Type II Radio Burst Within a Coronal Mass Ejection

Abstract

Solar type II radio bursts are generated through plasma emission caused by energetic electrons that are accelerated by shock waves during solar eruptions. These bursts serve as tracers of shock waves in the corona. However, the complexity of solar eruptions and the lack of radio imaging observations have hampered our understanding of type II bursts. The newly built Daocheng Solar Radio Telescope (DSRT) detected a rare type II burst. Its harmonic shows an initial herringbone (HB), followed by three nearly parallel lanes. These lanes form a framed pattern: a central main lane (termed MAIN) with a higher brightness temperature and wider bandwidth, flanked by two well-defined fringes, F1 and F2. Radio and extreme ultraviolet imaging observations indicate that the sources of the HB are precisely located on the flank of the leading shock wave driven by a coronal mass ejection (CME). In contrast, the MAIN and F2 sources correlate in terms of time, location, electron number density, and propagation velocity with an ascending coronal loop. In contrast, the F1 sources are associated with a nearby but distinct coronal loop. These observations suggest that at least three sources of the type II burst accompany the CME. A scenario involving multiple shock waves within the CME is proposed to explain the presence of the different radio sources.