Investigation of Thermospheric Horizontal and Vertical Neutral Winds via Tristatic Observations Over Alaska

Thermospheric-neutral winds in the F-region play a key role in the magnetosphere-ionosphere-thermosphere coupling system of the Earth. In this study, we reconstruct the full components of the thermospheric neutral winds, horizontal and vertical winds, using tristatic observations of line-of-sight (LOS) winds obtained from three Scanning Doppler Imager (SDI) instruments over Alaska. With the reconstructed neutral winds, we examine the meso-scale structures of 3D neutral winds inside the common volume of tristatic observations during the auroral activities observed by Time History of Events and Macroscale Interactions during Substorms (THEMIS) All Sky Imagers (ASI). Compared to the horizontal wind derived by the monostatic fitting, our reconstruction method provides better agreements of neutral wind features shown in LOS winds, including spatial maps of vertical winds. Our results also show the nonuniform wind flows in both horizontal and vertical directions during the auroral activities with fluctuations in both components within a few tens of minutes. The results indicate that the vertical and horizontal winds have more meso-scale features and rapid variations within the smaller horizontal domain (100 s of km) than those seen in earlier studies. The results also imply that the ion-neutral coupling plays an important role in generating the meso-scale structures of neutral winds.