Non-Maxwellian velocity distribution functions and incoherent scattering of radar waves in the auroral ionosphere

For studies of the high-latitude ionosphere it is important to calculate the effect of convection electric fields on the velocity distribution functions. At an altitude where the plasma is weakly ionized, the appropriate Boltzmann equation is solved in the spatial homogeneous case. The characteristics of the ion nonequilibrium steady state reached for large electric fields are discussed from the macroscopic point of view. From the microscopic point of view, it is shown that the Grad expansion fails to converge rapidly for large electric fields. Generalized polynomial expansions are developed for different models of ion-neutral interactions. The consequences of these non-Maxwellian ion distribution functions on radar waves are presented, and erroneous interpretations of measurements are discussed.