ABSTRACT

Earth's upper atmosphere at altitudes above 100-km is subjected to highly variable weather. Observations of this region, known as the thermosphere, commonly show long periods (days to weeks) of relatively placid conditions, punctuated by large disturbances that can only be described as "storms". However, even quiet times exhibit a substantial and often seemingly random background of day-to-day variability. In the troposphere, large storms develop internally, without a requirement for sudden impulsive changes by externally imposed forcing or regional boundary conditions. While internal instability does also play a role in Earth's ionosphere and thermosphere (especially at low latitudes); much of the thermospheric weather is instead directly driven from outside by forcing from regions above and below. Upward propagating waves and tides make a ubiquitous contribution to the low-level day-to-day variability, whereas fluctuations in the solar radiation, solar wind, and Earth's magnetosphere dynamics drive a broad spectrum of thermospheric perturbations - and are entirely responsible for driving storms and other large events.

The primary goal of this project is to understand the origins of day-to-day fluctuations in thermospheric weather, both large and small. Two state-of-the-art remote sensing instruments measuring thermospheric wind and temperature will be deployed in Antarctica, at latitudes that have been shown by previous studies to host the most extreme and complex thermospheric weather behavior. While previous work has measured thermospheric winds and temperatures across the globe for many years, there have never been instruments at these geomagnetic latitudes with anything even close to the proven sensitivity, resolution, and field of regard that are achieved by the proposed all-sky imaging design. Demonstrated performance of these new Fabry-Perot Spectrometers exceeds that of the previous generation of instruments at the Antarctic McMurdo and South Pole stations by more than two orders of magnitude, which will open revolutionary new insights in the fluid dynamics of Earth's polar-cap thermosphere.

This award will address a number of specific outstanding questions of aeronomical research: What is the main source of complex day-to-day variability that has been observed in the generally anti-sunward neutral flow across the polar cap? What are the mechanisms responsible for discrepancies between observed and modeled temperatures and tidal amplitudes within the polar cap? Do thermospheric gravity waves, propagating poleward from the auroral oval, deposit a significant flux of heat and/or momentum into the polar cap thermosphere? Are there any signatures of anthropogenic climate change and/or declining solar activity in the long-term record of thermospheric temperatures at South Pole?

Cutting-edge science, international partnership, and travel to Antarctica provide an ideal opportunity to achieve the project's education and outreach goals. Anticipated broader impacts from this project include training of a Ph.D. graduate student, furthering international scientific collaboration and cooperation in Antarctica, and providing real-time and archive data that will be of operational value to satellite operators, communicators, and navigators.

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