The incoherent scattering of radio waves in a non‐Maxwellian plasma: The effects of Coulomb collisions

In this paper the formulas for the ion distribution as well as the spectrum of radio waves scattered in a magnetized plasma with a strong electric field are derived. It is shown that the presence of the electric field in the ionosphere leads to an anisotropic ion velocity distribution and, therefore, to untypical incoherent scatter spectra for the F region of the polar ionosphere which are caused by ion‐neutral together with ion‐ion collisions. The effect of ion‐ion collisions, which has not been taken into account so far, is to reduce the anisotropy of the ion velocity distribution. Estimates of the ion‐ion collision frequency derived from EISCAT measurements show that this may happen above about 300 km.