Kinetic theory of the Farley‐Buneman instability in the <i>E</i> region of the ionosphere

Abstract

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 earlier which takes into account such important factors as the non‐Maxwellian nature of the perturbed electron distribution, different rates for electron momentum and energy relaxation, and the velocity dependence of the electron‐neutral collision frequency. The dispersion relation obtained using this theory is applicable for wave frequencies small compared to the ion‐neutral collision frequency and for sufficiently low altitudes where the electron‐electron collisions are negligible. The threshold conditions prove to be strongly modified compared to those resulting from the earlier simplified theories. For strong electric fields which can occur in the auroral regions, unstable long‐wave waves excited along the bisector between the directions of the electric field E 0 and E 0 ×B drift velocity are predicted at low atitudes. The excitation of such waves becomes possible due to a new kinetic mechanism associated with the perturbed electron current caused by the Pedersen conductivity.