Simulations of spectral asymmetries of pure two-stream waves in the equatorial electrojet

The nonlinear quasi-steady state of the Farley-Buneman two-stream wave obse rved in the E region ionosphere at altitudes in the range of 95-110 km is s tudied by numerical simulation. The behavior of this two-stream wave in the plane perpendicular to the Earth's magnetic field is simulated with a two- dimensional two-fluid code in which the electron inertia is neglected while the ion inertia is retained. We found that, for the waves with wavelength well above (smaller than) 3 meters, the most intense waves propagate in the (k) over right arrow . (E) over right arrow (0) < 0(<(k)over right arrow> . (E) over right arrow (0) > 0) region. The simulation result of up-down as ymmetry for the 3-meter wave is consistent with the radar observations. Fro m the simulations, we conclude that the background polarization electric fi eld driving the elctrojet is responsible for the spectral asymmetries.