CEDAR: Solar Extreme Ultraviolet Irradiance Effects on the Coupled Ionosphere-Thermosphere System

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The Coupling, Energetics, and Dynamics of Atmospheric Regions (CEDAR) program is a broad-based, community-guided, upper atmospheric research program. It is aimed at understanding the behavior of atmospheric regions from the middle atmosphere upward through the ionized upper layers of the atmosphere and into outer space in terms of coupling, energetics, chemistry, and dynamics on regional and global scales. The processes of interest are related to perturbations that propagate upward from the lower atmosphere as well as to solar radiation and particle inputs from above. This project will contribute fundamental results towards CEDAR goals in the area of understanding the variability in the upper atmosphere caused by the changing input of solar irradiance in the extreme ultra-violet part of the spectrum. A specific goal is to determine directly, for the first time, the relationship between measured irradiance levels and observed conditions in the upper atmosphere. The results of this study will provide a unique observational benchmark for validating and constraining physics-based models of the upper atmosphere. Such models are essential for understanding and predicting critical processes in the near-Earth space environment that can severely impact technological systems such as satellite navigation, radio wave communication, and electric power grids. The project will support the education of a graduate student at University of Texas at Dallas. The main goal of this project is to quantify the response of the ionosphere relative to direct, spectrally separated measurements of solar extreme ultraviolet (EUV) radiation from the TIMED and SDO spacecraft. This approach constitutes an immense improvement over previous studies based on proxies. The C/NOFS and DMSP spacecraft will provide corresponding measurements of ionospheric parameters at a range of altitudes. This dataset, spanning more than a solar cycle, allows for the use of advanced statistical analysis techniques and will be used together with the SAMI-2 model to address outstanding science questions related to understanding the ionospheric response to solar EUV variability. Interesting questions to be investigated include the relative importance of and interaction between the responses in the neutral and ionized components of the upper atmosphere.