KINETIC-THEORY OF THE FARLEY-BUNEMAN INSTABILITY IN THE E-REGION OF THE IONOSPHERE

The linear stage of the Farley-Buneman instability in the ionospheric E region is reexamined, Unlike previous theories, the present analysis is based on a consistent kinetic theory for electrons developed earli er which takes into account such important factors as the non-Maxwelli an nature of the perturbed electron distribution, different rates for electron momentum and energy relaxation, and the velocity dependence o f the electron-neutral collision frequency. The dispersion relation ob tained using this theory is applicable for wave frequencies small comp ared to the ion-neutral collision frequency and for sufficiently low a ltitudes where the electron-electron collisions are negligible. The th reshold conditions prove to be strongly modified compared to those res ulting from the earlier simplified theories. For strong electric field s which can occur in the amoral regions, unstable long-wave waves exci ted along the bisector between the directions of the electric held Eo and Eo x B drift velocity are predicted at low atitudes. The excitatio n of such waves becomes possible due to a new kinetic mechanism associ ated with the perturbed electron current caused by the Pedersen conduc tivity.