CURRENTS AND TURBULENCE IN AND NEAR MIDLATITUDE SPORADIC E-LAYERS CAUSED BY STRONG ACOUSTIC IMPULSES

The generation of Hall and field-aligned currents in and in the vicini ty of nighttime mid-latitude sporadic E-layers moving under the action of strong acoustic impulses of seismic, anthropogenic, or meteorologi cal nature is considered in a model presented in this paper. The influ ence of the electrical polarization fields caused by charges at the ho rizontal edges of the sporadic layers and the finite external circuits are also taken theoretical model is applicable for ionospheric altitu des between 95 and 130 km. The estimates show that under certain condi tions in a system with two sporadic E-layers, one of which is the curr ent generator and the other is situated in the external circuit, the F arley-Buneman instability could be generated. On the other hand, obser vations show that Farley-Buneman waves are likely responsible for the infrequent echoes of midlatitude 50-MHz backscatter with Doppler veloc ities near 300 m s(-1). The possibility exists that the proposed curre nt-generator model is at the origin of the observed mid-latitude Farle y-Buneman waves.