Theory of electrostatic fields in the ionosphere at polar and middle geomagnetic latitudes

Abstract

An analysis is presented of the properties of the elongated electrostatic fields that provide the coupling mechanism required in the dynamo-motor concept of the E and F regions of the ionosphere. This concept has been proposed in recent years to account for a variety of observed phenomena ranging from large-scale effects associated with tidal flows in the F region to small-scale effects associated with the scintillation of radio signals from radio stars or from space vehicles. The analysis is developed for an electrostatic field of arbitrary horizontal scale in a horizontally stratified partially ionized gas subject to an imposed magnetic field selected to be representative of conditions in polar and middle geomagnetic latitudes. The anisotropic character and continuous variation with height of the conductivity are retained throughout, and numerical solutions are determined for the attenuation of the electric field with height above the dynamo region. The results show that the attenuation is much less than that which would be experienced in a homogeneous medium, and that it is possible, for instance, for electrostatic fields having horizontal scale as small as about 3 or 4 km to extend from 130 km to 400 km with a loss in magnitude of only about 25 per cent. The results also show that relatively small changes in the ionospheric conditions, well within the range of possibilities, can result in very substantial changes in the attenuation of the electric field with height.