Height of the transition from O(+) ions to H(+) ions according to Aktivnyi-satellite data and the dependence of this height on solar activity

Variations of the height (h sub T) at which O(+) and H(+) concentrations are equalized are investigated on the basis of mass-spectrometric measurements of the ion composition of the topside ionosphere performed with the Aktivnyi satellite during a period of high solar activity. A dependence of h sub T on the F10.7 index is obtained for the total solar-activity cycle.