Numerical simulations of type II gradient drift irregularities in the equatorial electrojet

Two-dimensional numerical studies of the development of type II irregularities in the equatorial electrojet have been carried out using a method similar to that of McDonald et al. (1974) except that ion inertia has been neglected. This simplification is shown to be a valid approximation whenever the electron drift velocity is small in comparison with the ion acoustic velocity and the values of the other parameters are those appropriate for the equatorial E layer. This code enables us to follow the development of quasi-steady state turbulence from appropriate initial perturbations. The two-dimensional turbulent spectrum of electron density perturbations excited is studied both for the case of development from initial perturbations and for the case of a continuously pumped single driving wave.