Hot oxygen profiles for incoherent scatter radar analysis of ion energy balance

Thermospheric density and temperature are often derived from ionospheric observables measured by incoherent scatter radar (ISR) via solutions of the F region ion energy balance equation. However, this equation, consisting of an electron heat source balancing a neutral heat sink, can break down near the exobase, where the electron heat source can be too small by as much as 40%. An additional heat source is required, and theoretical and experimental studies point to a hot neutral oxygen (hot O) geocorona near the Earth's exobase to supply it. Hot O must therefore be included in the ion energy balance equation; however, its profile shape and concentration are unknown. We develop a simple method for including hot O profiles in the ion temperature fitting equation by calculating hot O concentration as a function of altitude and including the hot O heat source in the ion energy equation. The technique is tested as a function of solar cycle for March equinox conditions, and a χ 2 analysis indicates that the hot O is more likely to form a layer than a concentration profile which decreases as a function of altitude.