  An alternative mechanism is proposed for the generation of harmonics of the
electron plasma frequency due to the development of explosive instability in a
system of interpenetrating electron and proton flows in the solar atmosphere.
The efficiency of the new mechanism in comparison with the earlier discussed
mechanisms involving multistage processes of nonlinear interaction of waves in
plasma is determined. It is shown that the development of explosive instability
can lead to the excitation of the second and third harmonics of the plasma
frequency with comparable amplitudes.
