LOFAR Interferometric Observation of a group of Type III Solar Radio Bursts


Corona, the outermost layer of the Sun, is believed to permeate from a heliocentric distance of ~1.01 Rʘ to more than 1 AU. Being highly tenuous plasma medium, it harbours large scale structures, as multi-frequency observations reveal. One of the most common signatures of any flicker on the Sun is known as solar type III radio bursts. These bursts are an important diagnostic tool to understand the acceleration of non-thermal electron beams along the coronal magnetic field lines. Using the interferometric and beam formed capabilities of LOw Frequency ARray (LOFAR), we analysed a group of type III radio bursts observed between 80-20 MHz, on 30 March 2018. Taking advantage of the high spectral, temporal and spatial resolution of LOFAR, we were able to distinguish five different trajectories of propagation of the electron beams in the type III group. Using full Stokes observations (frequency and time resolution of 10 ms and 12 kHz, respectively) by the simultaneous beam formed LOFAR observations, we estimated the coronal magnetic field along these five electron beam trajectories. This was done by calculating the degree of circular polarisation of the harmonic plasma emission from the type III bursts. The methods and results will be discussed in this talk.

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