EAGER: Exploratory Measurements of Large Winds and Shears in the Lower Thermosphere and Their Variability Using an Enhanced Sodium Lidar

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The upper atmosphere near 120 km in altitude is an important transitional region where the dominant mixing processes change from interaction of small swirls or eddies (eddy diffusion) to interaction of individual molecules (molecular diffusion). This is also the part of the upper atmosphere that is notoriously difficult to observe since traditional ground-based techniques such as lidar generally cannot measure above 100 km due to low signal power and since satellites orbit at higher altitudes to reduce atmospheric drag. Occasional rocket measurements revealed unexpected large vertical and horizontal neutral wind and shears in this region. These winds are believed to be critically important in formation of intense and thin layers of metallic ions as well as in formation of critical layers that control dissipation and vertical propagation of atmospheric waves connecting different atmospheric layers. This project will provide first comprehensive measurements of large horizontal and vertical wind by using a state-of-the-art sodium lidar system operated by the Utah State University (USU). The project will improve public literacy by the USU lidar observatory participating in public outreach events in the Utah Cache Valley rural community. This project will also provide training for one graduate student and one undergraduate student at USU. The project will involve (1) replacement of interference filters which will improve the quality of the wind measurement by reducing the associated uncertainties by a factor of 2, (2) exploratory measurements with the enhanced USU sodium lidar equipped with large aperture (~5 m^2 receiving area), and (3) analysis of temporal variations and duration of strong winds and shears in the lower thermospheric region between 100 and 120 km in altitude.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.