  The conventional theory of resonance broadening for a two-species plasma in a
magnetic field is revised, and applied to an ionospheric turbulence case. The
assumptions made in the conventional theory of resonance broadening have, in
the past, led to replacing the frequency $\omega$ by
$\omega+ik_{\perp}^{2}D^{*}$ in the resonant part of the linear dielectric
function to obtain the nonlinear dielectric function. Where $D^{*}$ is an
anomalous diffusion coefficient due solely to wave scattering of the particle
orbits. We show that in general these assumptions are not valid, and
consequently the straightforward substitution of frequencies is not legitimate.
We remedy these problems and derive expressions for the time-dependent
components of the diffusion tensor. The improved resonance broadening theory is
developed in the context of an ionospheric problem, namely that of the
Farley-Buneman turbulence in the auroral E-region. A kinetic description of the
electrons is used. A general expression for the nonlinear dielectric function
is derived in the special case where no parallel electric field is present, and
the differences with the conventional dispersion relation are discussed.
