Stimulated scattering by collisional modes in the ionosphere

The excitation of low-frequency electrostatic waves by a high-frequency electromagnetic wave is investigated analytically, considering the case of stimulated scattering in the ionosphere at auroral latitudes. It is shown that the two-stream Farley-Buneman and collisional-drift modes can be nonlinearly excited at these latitudes because particle drift motions lower the threshold fields, to below the level pump of the field of the EISCAT incoherent-scatter-radar facility, for example. Although it may be difficult to interpret the experimental data, at least some of the modes in the thermal-fluctuation spectrum should be identifiable using incoherent-scatter techniques. 16 references