Midlatitude thermospheric wind and temperature: networked Fabry-Perot interferometer observations and radiative transfer modeling

This dissertation presents studies of the midlatitude and low-latitude thermosphere, primarily using networks of Fabry-Perot interferometers (FPIs). First, we describe an algorithm which estimates thermospheric line-of-sight wind and temperature from raw FPI data. This new algorithm has the advantage over previous work in that it provides accurate temperature estimates and uncertainties. We then present a novel regularization-based technique to estimate the thermospheric wind field from an FPI network's line-of-sight wind measurements. This technique makes no explicit assumptions about the functional form of the wind field, and instead lets the data inform the shape. We apply this technique to study the wind dynamics associated with the equatorial midnight temperature maximum, finding direct evidence of a converging wind field during its development. Next, we apply this technique to study the midlatitude thermospheric response to the geomagnetic storm of 01-02 Oct 2013. Though the horizontal wind and temperature measurements corroborate previous observations and theory in a broad sense, the downward vertical winds measured by six independent FPIs are unreasonably large (>100 m/s) and sustained (5 hours). A superposed epoch analysis of 15 different storms shows that such downward winds are commonly measured during the main phase. Using radiative transfer modeling, we show that these vertical winds are not real, and instead are artifacts of the scattering of airglow radiation in the lower atmosphere. This is the likely explanation for the large midlatitude vertical winds and horizontal convergences previously reported in the literature. We also show that some of the vertical winds repeatedly observed at equatorial latitudes may be explained as artifacts of atmospheric scattering. These results suggest that the effects of the lower atmosphere should be accounted for in any quantitative ground-based airglow measurement