4-D Ground Based Wind Mapping Technique to Resolve Altitude Variations of Neutral Wind Vectors in the Lower Thermosphere

This poster will provide details on a fundamentally new representation of thermospheric winds in a 3D volume solved over time. It also provides a brief update on new facilities being constructed in Scandinavia that will utilize this technique to support EISCAT 3D. Neutral winds in the lower thermosphere are of scientific interest (due to the transition from atmospheric behavior to space-like behavior) and of operational interest (because of their impact on radio propagation and on LEO spacecraft orbits, re-entry, and collision predictions). However, few techniques are available for measuring neutral winds at E-region altitudes, in the height range from approximately 120 to 220 km. In-situ probes are typically unable to remain aloft at these heights for more than a few hours, and remote sensing is largely ineffective in this range. Rocket-borne chemical release methods can provide absolute measurements for winds in this region; however, the cost and logistical effort of such experiments is too high for routine applications. In Alaska, the Doppler spectra of the oxygen 558 nm and 630 nm emissions from multiple all-sky viewing Fabry-Perot interferometers (FPIs) with overlapping fields of view have been combined and used to create a 3-component vector wind field resolved in four coordinate dimensions (three spatial, one temporal.) This technique starts with a base-line initial wind field that is easily generated from the data. The algorithm, referred to as the evolutionary algorithm, generates a sequence of random perturbations. A goodness of fit algorithm then determines how each perturbation should be applied to the initial wind field to best improve goodness of fit. This is repeated millions of times to generate the 4-D wind field. This poster explains the mathematical process in detail. University of Alaska Fairbanks is in the process of deploying three more instruments with overlapping fields of view in Scandinavia. This poster will show how locations of these instruments have been chosen to provide wind fields within the new EISCAT 3D volume to support ion neutral coupling studies.