Date of Award
Master of Engineering (ME)
Quantifying the spatial and temporal variability of nitric oxide (NO) emissions in the thermosphere using eigenmodes will increase the understanding of how upper atmospheric NO behaves, and could be used to increase the accuracy of future space weather and climate models. NO flux (NOF) from 100-250 km altitude taken from 13 years of data observed by the SABER instrument onboard the TIMED satellite is decomposed into four empirical orthogonal functions (EOFs) and their amplitudes to: 1) determine the strongest modes of NO flux variability (NOFV) in the data set, and 2) develop a compact model of NOF. The first four EOFs account for 83% of the variability in the data. Their uncertainty is verified using cross-validation analysis. The first EOF represents 69% of the total variance and correlates strongly with Kp and XUV flux, suggesting that geomagnetic activity and solar weather account for a large portion of NOFV. EOF 2 shows annual and seasonal variations, possibly due to annual and seasonal thermospheric composition and temperature changes, and may represent the chemical “breathing mode” of NOFV. EOF 3 shows annual variations and correlates with energetic proton flux, and is strongest after solar energetic particle events (SEPs) and X-flares. EOF 3 may represent winter time SEP-enhanced diurnal tide effects. EOF 4 suggests a transport mechanism toward the poles and outwards at the pre-dawn and post-dusk equator after strong storms. The NOF model is illustrated and the geophysical associations of the EOFs are discussed.
Flynn, Sierra Mae, "Understanding the Variability in Thermospheric Nitric Oxide Flux Using Empirical Orthogonal Functions (EOFs)" (2017). Aerospace Engineering Sciences Graduate Theses & Dissertations. 193.