Incoherent Scatter Radar Studies of Hot Oxygen

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This is a project to study hot oxygen in the upper atmosphere. The energy of solar photons absorbed in the upper atmosphere far exceeds the thermal energy of atmospheric particles (tenth of an eV). Thus, the atmosphere is immersed in a dilute sea of very energetic particles created by solar photon absorption. A prominent member of this collection of energetic particles is hot oxygen, a population of oxygen atoms found to be at a temperature of about 4000 K. This project studies hot O in two ways. First, the incoherent scatter radar (ISR) Data Base at the National Center for Atmospheric Research will be inspected for evidence of the heating effects of hot O. Ions in the topside ionosphere are hotter than classical theory says they should be, and hot O may possibly act as the missing heat source. The hot O density may be deduced from the temperature deficit between classical theory and measurement. The estimates of hot O will be developed into a model and of its behavior. Once the hot O model is established, it may be used to correct previous estimates of cold oxygen concentrations. Though this work explicitly concerns hot O determination and modeling, the longer term aim is to use the 30-year ISR data base to track cold O density throughout that period. If cold O changes from one 11-year solar cycle to the next it may indicate a measurable trend related to global change caused by changes in greenhouse gases or ozone at lower altitudes, changes which are expected to be amplified in atmospheric density at high altitudes. The second method is based on concentrations of hot oxygen ions. If there is neutral hot O, there must be hot oxygen ions present too. The ionosphere will be numerically simulated to determine what densities of hot O ions may be expected to exist in the ionosphere, given the model described above that will be developed for neutral hot O. Since helium ions at 1000 K and hot O at 4000 K have the same temperature-to-mass ratio, they cannot be distinguished by doppler radar techniques. The hot O simulation results will be compared with reported observations of helium ions in the topside ionosphere for likeness to determine if hot oxygen may have masquerading as helium in past published reports. The intellectual merit of the proposed project lies in the fact that it studies a little-known atmospheric species whose presence is expected, or has the potential, to explain a number of discrepancies between theory and observation, e.g., excess satellite drag, airglow, and ionospheric heating at high altitudes, and why satellite and radar measurements of oxygen density differ. The broader impacts of the project lie in several areas, in the integration of classroom and research activity, in the training of graduate and undergraduate students in the scientific process and presentation skills, in the involvement of under-represented groups, and in the provision to the scientific community a model of the behavior of hot O which should be useful in a variety of applications in which thermospheric and/or ionospheric mass or energy budget considerations are important.