Observations of electron temperature gradients in mid-latitude E sub s layers

Direct measurements of electron temperature were performed within mid latitude sporadic-E layers above White Sands, New Mexico, using a pulsed plasma probe. The probe's capability for unfolding density variations from its current-voltage characteristics made the temperature measurements possible within the steep density gradients characteristic of E(s) layers. The major feature of the observations was the presence of an electron temperature gradient across the layers: the bottom sides of the layers were isothermal at T(e) = 340 K while the topside of each layer showed T(e) increasing from 380 K to more than 500 K over a vertical extent of 400 meters. The results are discussed in terms of reversible heating by gravity waves as well as in terms of plasma density and ion composition effects within the ionospheric plasma itself.