Inferred temperature variations at theF2peak

Information on the ionospheric electron content deduced from the Faraday rotation of lunar radio reflections and ionospheric data obtained by vertical-incidence soundings are used to infer scale heights at the F2 peak. The scale height is found to exhibit pronounced time variations that are interpreted as variations in the temperature at the F2 peak. The average values of inferred scale heights at the F2 peak are compared with scale heights of a model atmosphere based on recent rocket and satellite data and are found to lie within ±15 per cent of the model values. One exception to this finding occurred on a day following a magnetic storm: on this day, the scale height was more than 30 per cent higher than the model value. This difference suggests the possibility of a pronounced increase in ionospheric heating at such times.