Solar radio type III bursts are believed to be the most sensitive signature of near-relativistic electron beam propagation in the corona .
A solar radio type IIIb-III pair burst with fine frequency structures , observed by the Low Frequency Array ( LOFAR ) with high temporal ( \sim 10 ms ) and spectral ( 12.5 kHz ) resolutions at 30 - 80 MHz , is presented .
The observations show that the type III burst consists of many striae , which have a frequency scale of about 0.1 MHz in both the fundamental ( plasma ) and the harmonic ( double plasma ) emission .
We investigate the effects of background density fluctuations based on the observation of striae structure to estimate the density perturbation in solar corona .
It is found that the spectral index of the density fluctuation spectrum is about -1.7 , and the characteristic spatial scale of the density perturbation is around 700 km .
This spectral index is very close to a Kolmogorov turbulence spectral index of -5 / 3 , consistent with a turbulent cascade .
This fact indicates that the coronal turbulence may play the important role of modulating the time structures of solar radio type III bursts , and the fine structure of radio type III bursts could provide a useful and unique tool to diagnose the turbulence in the solar corona .