Ion composition in sporadic <i>E</i> layers measured by the EISCAT UHF radar

Abstract

We present ion composition results for several sporadic E layers observed during a Norwegian special program carried out by the European Incoherent Scatter Facility (EISCAT) UHF radar in August 1984. A range resolution of 600 m was used. Eight sporadic E layers at altitudes 95–114 km were studied using various fitting strategies for obtaining the ion composition. A fixed temperature was assumed in some of the strategies; in others the temperature was fitted together with the composition. Heavy ions, most probably Fe + , were found to be present in most layers with relative abundances of 30–80%. In one case, the composition analysis shows that essentially no heavy ions are present. This layer is supposed to be composed of light metal ions, such as Mg + . In one particular event a layer is seen to separate into two sheets with a height difference of 2–3 km, and the ion compositions in the two parts are found to be different. Possible explanations of this phenomenon are discussed.