A Wave-driven Nonlinear Current in the E-region Ionosphere

Ionospheric two-stream waves and gradient-drift waves nonlinearly drive a large-scale (D.C.) current in the E-region ionosphere. This current ows parallel to, and with a comparable magnitude to, the fundamental Pedersen current. The underlying mechanism is quite simple. E-region plasma waves generate oscillating electric elds causing electrons to ~ E ~ B drift perpendicular to the wave's propagation direction. On the wave's maxima, electrons drift with the same velocity but in the opposite direction as they do on the minima. Since more electrons exist at the maxima than at the minima, a net current results. Wave-driven currents will substantially modify the large scale dynamics of the E-region during highly active periods. They will aaect the behavior of E-region waves, possibly causing type I radar echoes to have a Doppler velocity close to the acoustic speed. Additionally, wave-driven currents may be the source of non-sinusoidal electric eld measurements made in gradient-drift waves by rockets.