Session 7E - Space and Basic.
ORAL session, Thursday morning, November 14
Majestic Ballroom, Adam's Mark
Ionospheric two-stream waves and gradient-drift waves nonlinearly drive D.C. currents in the E-region ionosphere. These currents flow parallel to, and with a comparable magnitude as, the fundamental Pederson current, acting to discharge the electrojet. The fundamental mechanism of this instability is quite simple. E-region plasma waves generate oscillating electric fields which cause electrons to \vec E \! \times \! \vec B drift perpendicular to the wave propagation direction on the density maxima and minima of the waves. On the maxima these 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 the minima, a net D.C. current results. This wave-driven current can be of the same order of magnitude as the fundamental ion-Pederson current, modifying the large scale dynamics of the E-region during highly active periods. It may also be responsible for a number of observed features of E-region waves, including the oft-repeated radar observation that equatorial Farley-Buneman waves travel at the acoustic velocity as well as the squaring-off of gradient-drift waves observed by rockets.