  Type III solar radio bursts are generated by streams of energetic electrons
accelerated at the Sun during periods of the solar activity. The generation
occurs in two steps. Initially, electron beams generate electrostatic Langmuir
waves and then these waves are transformed in electromagnetic emissions. It is
widely accepted that the mechanism of generation of emission on fundamental
frequency close to plasma frequency is due to induced scattering of Langmuir
waves into electromagnetic. However this process imposes quite restrictive
limit of the ratios of effective brightness temperatures of electromagnetic and
Langmuir waves in the source region. Recent studies showed that the level of
density fluctuations in the solar wind and in the solar corona is so high that
it may significantly affect beam-plasma interaction. Here we show that the
presence of intense density fluctuations not only crucially influence the
process of beam plasma interaction but also changes the mechanism of energy
transfer from electrostatic waves into electromagnetic. Reflection of the
Langmuir waves from the density inhomogeneities may result in partial
transformation of the energy of electrostatic wave into electromagnetic. We
show that the linear wave energy transformation for the level of fluctuations
of the order of 1\% or higher may be significantly more efficient for
generation of type III solar radio bursts than conventionally considered
process of nonlinear conversion due to induced scattering on ions.
