Incoherent scattering of radar waves from nonthermal F region plasma: Analytical methods of spectrum synthesis

A new method is presented of computing the theoretical spectrum of the incoherent scatter signal from nonthermal ionospheric F region plasma. An expression for the ion line‐of‐sight velocity distribution function is derived analytically and the evaluation of the Cauchy principal value integral, part of the longitudinal dielectric function, is discussed. Spectra revealing the presence of nonthermal plasma have recently been observed by the European Incoherent Scatter (EISCAT) radar during periods of rapid plasma flow, and the incorrect assumption of Maxwellian plasma at such times will cause errors in the plasma density and temperatures derived. The new procedure is tailored to satisfy the needs of non‐Maxwellian spectral analysis of data from EISCAT and other incoherent radar systems.