Collaborative Research: Anomalous Plasma Cooling in the Topside Ionosphere During Solar Eclipses

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Previous observations during the 2017 solar eclipse in the weakly ionized portion of the upper atmosphere (the ionosphere) revealed a surprising result. Rather than the expected smooth response to the Moon's shadow, the electron and ion temperatures observed by two satellites traversing the topside ionosphere at 850 km in altitude showed complex and sporadic jumps between regions of cooler plasma and regions where the temperatures were nominal. This project will investigate these unexpected plasma temperature modulations by conducting a thorough analysis of the plasma observations (temperatures, density, flows) for this and other past eclipse events. This will provide important information about how the ionosphere responds to the transient changes in the illumination drivers. Knowledge of these responses is important since solar illumination is a key driver of fundamental processes of ionization and structuring. Radio propagation through the ionosphere depends on how much ionization and structuring occurs, and solar eclipses provide a controlled and quantifiable way to learn more about both positive and adverse effects of the ionosphere on global networks that use radio frequencies, for example the Global Navigation Satellite System. This project will provide detailed characterization of the ionospheric plasma anomalies during solar eclipses using Defense Meteorological Satellite Program measurements of the plasma density, electron and ion temperatures, and plasma transport. It will also provide identification and characterization of mutual relationship between the irregular solar source regions and consequential ionospheric transient modulation. Finally, the project will identify the physical mechanisms, controlling parameters, and limiting cases of the anomalous flows and temperatures. The ultimate goal of this work is to obtain a better understanding of how short-term changes in the illumination of the dayside ionosphere can produce non-uniform responses in the ionospheric density, temperature, and drifts.This project will contribute to the development of a highly-skilled workforce by supporting a graduate student at Boston University.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.