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The size of radio emission sources at the plasma frequency in the solar corona is thought to be fundamentally limited by scattering off of random density inhomogeneities. Radio interferometers such as the LOw Frequency ARray (LOFAR) have been increasingly used to study radio bursts in the solar corona over the last number of decades.
Observations with LOFAR’s tied-array imaging technique suggest that the source sizes of Type III radio burst emission is limit by coronal scattering. However, it has yet to be determined whether source sizes observed with tied-array imaging are a result of this fundamental limit or an effect due to interpolation used in that imaging mode.
LOFAR interferometric imaging gives another measure of source size and its resolution can be much finer. Here, an interferometric dataset of a Type IIIb burst (a Type III burst showing frequency striations) observed with an 86 km baseline is analysed. We show that despite a sub arc minute resolution coronal source sizes are significantly larger than expected from analysis of fine structure in the burst spectrum further supporting the theory of scattering being the limiting factor in coronal radio observations.