Derivation of neutral oxygen density under charge exchange in the midlatitude topside ionosphere

摘要: [1] We describe a new technique to derive neutral atomic oxygen density, [O], in the upper thermosphere using coincident incoherent scatter radar (ISR) and airglow emission observations from Arecibo Observatory. The exploits nearly resonant charge exchange coupling between ionized hydrogen that serves as dominant chemical source sink of protons near above F region peak. Under production loss H+, proton continuity equation can be solved for [O] twilight H density profiles derived measured brightness at 656.3 nm together with ion temperature, flux obtained simultaneously by ISR. We present both equilibrium nonequilibrium solutions 500 1500 km during single quiescent nighttime interval under moderate solar activity. Comparisons theoretical expectations MSIS-model calculations O are used identify altitude local time extent over which is justified. These comparisons generally support validity ∼600 800 km, where sufficient reactant densities validate formulation equation. Equilibrium 650–700 exhibit excellent agreement MSIS estimates before midnight, but deviations arising transport become increasingly significant this height dawn approaches. Incorporation gradients into improves modeled significantly after while minor contributions several hours midnight lend additional presence equilibrium.