Estimation of electron density in the nighttime ionosphere based onremote sensing of the 135.6 nm far ultraviolet emission

Ionosphere;F-region;Electron density;Ionospheric Connection Explorer (ICON);Far ultraviolet;inverse problem

Iliou, Dimitrios ; Kamalabadi ; Farzad ; Makela ; Jonathan J.

关键词: Ionosphere;    F-region;    Electron density;    Ionospheric Connection Explorer (ICON);    Far ultraviolet;    inverse problem;   

Others  :  https://www.ideals.illinois.edu/bitstream/handle/2142/92857/ILIOU-THESIS-2016.pdf?sequence=1&isAllowed=y

美国|英语

来源: The Illinois Digital Environment for Access to Learning and Scholarship

【 摘 要 】

This thesis develops a method to accurately estimate the electron density altitude profiles of the nighttime ionosphere, as well as important parameters such as the peak height and density, using nighttime far ultraviolet (FUV) measurements of the 135.6 nm nighttime emissions. Specifically, we will describe a method to accurately obtain the electron density content of the ionosphere by using brightness measurements of the nighttime 135.6 nm emission. The method is applied and tested using simulated measurements to relate to those to be obtained by the limb-viewing FUV instrument on board the Ionospheric Connection Explorer (ICON) satellite scheduled to be launched in 2017.The OI 135.6 nm emission can be used as a proxy of the ionosphere's electron density and is related through an integral equation of the volume emission rate to the brightness measured by the FUV instrument. The instrument's observation geometry allows for the discretization of the problem, thus connecting the ionosphere's electron density with the measured brightness through a matrix equation. Regularization methods are used in order to enforce constraints ofsmoothness and continuity on the estimation of the volume emission rate, to compensate for the noise amplification in the inversion process. Tikhonov regularization, generalized cross-validation, total variation and Bayesian methods that assume prior knowledge of the ionosphere's electron density distribution are investigated.Comprehensive simulations are used to explore the different brightness intensities for all longitudes, and for latitudes from -40 to 40 degrees, in order to allow the characterization of the effect of different SNR values on the electron density reconstruction accuracy. FUV measurements are simulated using the International Reference Ionosphere (IRI) and Mass Spectrometer and Incoherent Radar (MSIS) models to create a forward model which can be inverted in order to validate the altitude profile reconstruction as well as the peak height and density accuracy. This allows us to investigate the expected performance of the FUV instrument.