Incluye bibliografía

1. Introduction -- 2. Simulation models -- 3. Model A - Simulation results and discussion -- 4. Model B - Simulation results and discussion -- 5. Conclusions

The nonlinear state of the two-stream plasma instability in the equatorial electrojet has been investigated using nonlinear two-dimensional computational models. The models employed the two-fluid equations for electrons and ions under the influence of an applied electric field perpendicular to a constant northward magnetic field. Collisions with neutral species were included, along with a viscous representation of the Landau damping of short wavelength modes. The unperturbed plasma was assumed to be homogeneous and isothermal. The simulation confirmed radar observations of isolated Type I irregularities of Crochet et al. (1979): a) horizontally directed waves were dominant and propagated at the acoustic speed, and b) obliquely-directed waves were less intense by several orders of magnitude and propagated at speeds lower than the acoustic speed. The instability appeared to saturate when the angle, 0, between the dominant wave vector and the current density, <J> cos 0 decreased to a critical value Jo