Source size and Position of a Type IIIb-III Pair with LOFAR

Solar radio bursts originate mainly from high energy electrons accelerated by solar eruptions like solar flares, jets, and coronal mass ejections (CMEs). A sub-category of solar radio bursts with a short time duration may be used as a proxy to understand the wave generation and propagation within the corona. Complete case studies of the source size, position, and kinematics of short-term bursts are very limited due to instrumental limitations.LOw-Frequency-ARray (LOFAR) is an advanced radio antenna array. It is capable of a variety of processing operations including correlation for standard interferometric imaging, the tied-array beam-forming, and the real-time triggering on incoming station data-streams. With recently upgraded LOFAR, we can achieve high spatial and temporal imaging for solar radio bursts.Here we present a detailed analysis of the fine structures in the spectrum and of the radio source motion with imaging, the radio source of a type IIIb-III pair was imaged with the interferometric mode using the remote baselines of the (LOFAR). This study shows how the fundamental and harmonic components have a significant different source motion. The apparent source of the fundamental emission at 26 MHz is about 4 times the speed of light, while the apparent source of the harmonic emission shows a speed of < 0.02 c. We show that the apparent speed of the fundamental source is more affected by the scattering and refraction of the coronal medium.