Ion-acoustic instability in the ionospheric E-region

The exact analytical solution of the dispersion equation for electrostatic waves in a uniform plasma of the ionospheric E-region is considered. Proceeding from this solution, it is shown that the ion-acoustic instability can develop at angles alpha < 1 degrees, where sin alpha = k(z)/k. The possibility of applying the ion-acoustic instability to interpreting type I and type 4 events of coherent radar scattering is discussed. It is shown that the consideration of the Landau damping for ion-acoustic waves does not hinder the development of the ion-acoustic instability under the conditions of the E-region if the ratio of the electron and ion temperatures T-e/T-i >= 2.3.