Effect of short scale turbulence on kilometer wavelength irregularities in the equatorial electrojet

The kilometer-scale irregularities in the daytime equatorial electrojet are studied within the framework of a two-fluid, quasilinear, nonlocal theory of the gradient-drift instability. The effect of the short scale turbulence is included into the large scale equations through turbulent mobility and diffusion operators obtained from a quasilinear treatment of the electron equations. The turbulent mobility is determined as a function of altitude in terms of the small scale density fluctuation spectrum, and its peak equals a few times the classical Pedersen mobility value. The equilibrium solutions of the large scale equations are derived in the presence of the short wavelength turbulence. The localization of the unstable modes and of the current layer is seen to shift towards higher altitudes and the current density profile conforms well with some of the available experimental data. The local and nonlocal linear growth rates of the long wavelength modes are also obtained and discussed. The nonlocal linearized equations for the large scales are integrated numerically and the effects of the turbulent mobility and of velocity shear are discussed