MIDLATITUDE SPORADIC-E LAYERS.

It is the purpose of this work to examine the structure and motion of sporadic-E layers in detail, both in the vertical and horizontal planes, in the context of the present theory of the formation of these layers. The following are the main conclusions arrived at through this study: Gradient reflections are not important in ionosonde observations of sporadic-E. Small-scale horizontal structure exists in midlatitude sporadic-E layers. The features of sporadic-E layers observed by incoherent-scatter radar are found to be consistent with layers composed of metallic ions being acted on by the motions of the neutral atmosphere as described by wind-shear theory. The irregular structure observed in midlatitude sporadic-E layers is mainly determined by the motions of the neutral atmosphere. Intense localized irregularities indicate the proximity of critical levels in the internal-gravity-wave spectrum.