Estimation of Thermospheric Oxygen Density and Temperature From Combined Optical and Radar Measurements

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Neutral atomic oxygen, O, is a key species in Earth's upper atmosphere, where it dominates thermospheric composition between ~200-700 km. Knowledge of its density, [O], is required for spacecraft operations in low earth orbit, for understanding the coupling between the thermosphere and ionosphere, and for characterizing the dynamic atmospheric response to drivers such as space weather or climate change. This project is to develop a new technique for [O] estimation based on Incoherent Scatter Radar (ISR) data and coincident optical emission observations. The new technique will provide both O density and temperature estimates over the altitude range 550-850 km. It bases the [O] estimation on O and H+ rather than O and O+ coupling, thereby avoiding the difficulties associated with uncertainties in the O+-O collisional cross section that have plagued traditional ground-based techniques in the past. This is made possible by new incoherent scatter multi-ion fitting techniques recently developed at Arecibo for the topside ionosphere. The technique will be applied to nearly 20 years of optical and radar data available from the Arecibo observatory to compile a climatology of mid-latitude [O] and temperature variations for the thermosphere. New measurements facilitating improvements in optical detector sensitivity and dual-beam radar capability at Arecibo will be used to extend the altitude range of the neutral density inversions down to lower altitudes. This will allow for an independent, much improved estimation of the so-called "Burnside factor", F, a measure of the discrepancy between theoretical and empirical estimates for the O+-O collision frequency. The large discrepancies in existing estimates of this factor constitute a long-standing puzzle in thermosphere chemistry. Broader impacts of this project include the usefulness of this new technique for a wide range of other atmospheric studies. In addition, the project includes research opportunities for students and would help further the independent research career of a young, successful female scientist.