Date of Award
Doctor of Philosophy (PhD)
Electrical, Computer & Energy Engineering
Francis G. Eparvier
Albin J. Gasiewski
Solar extreme ultraviolet (EUV) radiation is a primary driver of space weather at Earth and Mars. At Earth, this radiation can affect satellite drag and disrupt communication and navigation signals. At Mars, it contributes to the loss of a once dense atmosphere to space. Recent EUV irradiance instruments, such as the EUV Monitor (EUVM) on the Mars Atmosphere and Volatile EvolutioN (MAVEN) orbiter and the EUV and X-ray Irradiance Sensors (EXIS) on the next generation Geostationary Operational Environmental Satellites (GOES) use multi-spectral sensors to measure key portions of the EUV spectrum which drive models to estimate the complete EUV spectral irradiance. This thesis develops new models for use by EUVM and EXIS using three distinct methods. 1) Empirical models use predetermined correlations with available measurements to estimate the spectral irradiance. I use new high resolution and high time cadence measurements from the EUV Variability Experiment (EVE) on the Solar Dynamics Observatory (SDO) to improve model spectral resolution and reduce uncertainty. I develop the FISM-M model for MAVEN and the L1B Operational Model for EXIS, each with 5-10% typical uncertainties. 2) Semi-empirical models reconstruct the spectrum by weighting a set of reference spectra according to solar activity estimated with broadband measurements. The SynRef model is developed for EUVM to improve the spectral resolution by 10-100X from 0-6 nm. A semi-empirical model is also developed for the solar H Lyman-_ line using newly published 1.5 picometer resolution spectra from SOHO/SUMER, and is used to retrieve Mars H-corona densities from EUVM occultation measurements. 3) I develop the Lumped Element Thermal Model (LETM) for specifically modeling the time evolution of EUV are emissions. I show that hot and cool EUV are emission light curves are related through the low pass filter equation. This new effect is used to motivate a simple are cooling model which can accurately reproduce the light-curves of cooler EUV emissions with commonly available measurements. Although the models developed here are for the EUVM and EXIS instruments, the underlying methods can be applied to comparable multi-spectral platforms; past, present and future.
Thiemann, Edward M.B., "Multi-Spectral Sensor Driven Solar EUV Irradiance Models with Improved Spectro-Temporal Resolution for Space Weather Applications at Earth and Mars" (2016). Electrical, Computer & Energy Engineering Graduate Theses & Dissertations. 130.