In the earth's ionosphere the presence of nonthermal electrons causes enhancement of the electron plasma line resonance observed by incoherent backscatter radar. This paper extends previous calculations of the plasma intensity by including resonance broadening due to electron-neutral collisions. A BGK collision term is included in the derivation of the electron spectral density function obtained from fluctuation dissipation theory. Assuming the nonthermal electron distribution is a small perturbation on a Maxwellian distribution of background electrons, the expression describing the signal intensity for a plasma line reduces to the form obtained previously when only electron-ion collisions were included. Results of this extended model are compared to recent measurements made with the Chatanika radar. |