Currents and turbulence in and near mid-latitude sporadic E-layers caused by strong acoustic impulses
The generation of Hall and field-aligned currents in and in the vicinity of nighttime mid-latitude sporadic E-layers moving under the action of strong acoustic impulses of seismic, anthropogenic, or meteorological nature is considered in a model presented in this paper. The influence of the electrical polarization fields caused by charges at the horizontal edges of the sporadic layers and the finite conductivity of the external circuits are also taken into account. The theoretical model is applicable for ionospheric altitudes between 95 and 130 km. The estimates show that under certain conditions in a system with two sporadic E-layers, one of which is the current generator and the other is situated in the external circuit, the Farley-Buneman instability could be generated. On the other hand, observations show that Farley-Buneman waves are likely responsible for the infrequent echoes of mid-latitude 50-MHz backscatter with Doppler velocities near 300 m s –1. The possibility exists that the proposed current-generator model is at the origin of the observed mid-latitude Farley-Buneman waves.