Abstract: Solar radio observations provide a unique diagnostic of the outer solar atmosphere. Here I report quantitative spatial and frequency characterization of solar radio burst fine structures observed with the Low Frequency Array (LOFAR). The observations demonstrate that radio wave propagation effects, and not the
properties of the intrinsic emission source, dominate the observed spatial characteristics of radio burst images.
The observed spectral characteristics of the fine structures are consistent with the model involving modulation of the type III burst emission mechanism by small-amplitude fluctuations of the plasma density along the electron beam path.