Source Imaging of a Moving Type IV Solar Radio Burst and Its Role in Tracking Coronal Mass Ejection from the Inner to the Outer Corona

Abstract

Source imaging of solar radio bursts can be used to track energetic electrons and associated magnetic structures. Here we present a combined analysis of data at different wavelengths for an eruption associated with a moving type IV (t-IVm) radio burst. In the inner corona, the sources are correlated with a hot and twisted eruptive EUV structure, while in the outer corona, the sources are associated with the top front of the bright core of a white-light coronal mass ejection (CME). This reveals the potential of using t-IVm imaging data to continuously track the CME by lighting up the specific component containing radio-emitting electrons. It is found that the t-IVm burst presents a clear spatial dispersion with observing frequencies. The burst manifests broken power law-like spectra in brightness temperature, which is as high as 10⁷-10⁹ K, while the polarization level is generally weak. In addition, the t-IVm burst starts during the declining phase of the flare with a duration as long as 2.5 hr. From the differential emission measure analysis of AIA data, the density of the T-IVm source is found to be at the level of 10⁸ cm^-3 at the start of the burst, and the temperature may reach up to several MK. These observations do not favor gyrosynchrotron to be the radiation mechanism but are in line with a coherent plasma emission excited by energetic electrons trapped within the source. Further studies are demanded to elucidate the emission mechanism and explore the full diagnostic potential of t-IVm bursts.