The LOFAR observation of Type III radio burst

© Peijin Zhang, Pietro Zucca

Solar Type-III radio burst is a kind of strong radio burst with fast drift rate. It is excited by the energetic electrons injected into the corona through open magnetic-field lines rooted in active regions. The characteristic of the radio burst received by an observer is highly related to the property of the electron beam and the fluctuating plasma in the corona. Type-III radio burst can help us understand how energy is released by the active Sun, and also help study the plasma in the solar corona.

Using the high temporal and spatial resolution of LOFAR, we were able to image the Sun at a rate of 6 frames per second with an angular resolution of about 20 arcsec. With this resolving power, we can see the shape and movement of the radio source at different frequencies, which correspond to the energetic electron in various layers of the corona.

The left panel of this image shows the dynamic spectrum of a typical type III radio burst, several colored dots on the scanning line marks the frequencies used for imaging. The right panel shows the interferometric image of the sun during the type III burst, the colors indicate the frequencies according to the dots in the left panel.