CEDAR: Investigating Helium Behavior and Its Role in the Thermosphere

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This project addresses fundamental physical processes that govern the behavior of helium throughout the thermosphere and also elucidates its role in understanding the behavior of other thermospheric constituents. The thermosphere is the domain for many low-earth-orbiting satellites and the constituent makeup, their transport properties, and their bulk motion contribute significantly to satellite drag. Helium has been a missing constituent in current thermosphere general circulation models and plays an important role in determining satellite drag effects in the upper thermosphere through its impact on the total mass density. Additionally helium is an excellent dynamical tracer creating the possibility of using helium observations to describe the poorly measured wind systems in the thermosphere. The project addresses ways of understanding complexity in the geospace system and will be carried out as a collaboration between the University of Colorado and NCAR. Two graduate students will be involved in the project. Through this award, the implementation of a scheme to fully describe helium structure in altitude, latitude, longitude, local time, season, solar cycle and geomagnetic activity in NCAR community models will be completed. This new scheme will then be used to evaluate the processes responsible for the distribution and variation of helium. This understanding can then be projected to other gasses whose overall structure and behavior are complex but, by contrasting with helium, can be evaluated for its transport dependencies. The dynamical influences on composition also impact estimates of total mass density, where helium during solar minima can have a direct contribution. This work will lead to a better characterization of the thermosphere and can be used to improve satellite drag studies. Model output will be compared with satellite observations for evaluation.