Four-dimensional reconstructions of thermospheric vector wind fields using multistatic Doppler spectra of optical emissions at 558 and 630 nm.

The thermospheric wind is a vector field that varies in four dimensions - zonal, meridional, vertical, and temporal. No existing experimental techniques have been demonstrated that resolve variations in all three vector wind components across all four of these dimensions. Here we explore techniques that could reconstruct the four-dimensional thermospheric vector wind field, using line-of-sight wind measurements obtained by a network of ground-based all-sky Fabry-Perot interferometers (FPI)observing Doppler shifts of the red (630 nm) and green (558 nm) optical emissions from atomic oxygen. During periods when these emissions are primarily excited by aurora, altitude profiles of their volume emission rate vary with characteristic energy of the auroral precipitation. This variation is especially prominent for the green line. As a result, under appropriate auroral conditions, the spectra recorded by the FPIs can sample a range of latitudes, longitudes, and altitudes over time. Further, it is possible to use Doppler temperature measurements to estimate the centroid height sampled by each individual green-line spectrum. Here we explore numerical techniques that can be used to exploit this four-dimensional sampling distribution to derive estimates of all three vector winds components throughout the 4D sample hyper-volume. We present example observational data, the technique used to reconstruct the 4D vector wind field from it, and show some preliminary results.