3-Dimensional Reconstruction of Thermospheric Neutral Wind Using Tri-Static Scanning Doppler Imagers in Alaska

Neutral winds in the thermosphere are important for understanding ion-neutral interaction in the ionosphere-thermosphere coupling system of the Earth. However, due to limitations of ground-based observations, studies for the vertical winds are confined to small local zenith angles. Also, the derivation of horizontal winds requires the assumption that the gradients along the meridional direction are small. In this study, we present a reconstruction method of 3-d full components of the neural wind in the |843 × 592| km horizontal domain using line-of-sight winds obtained by three Scanning Doppler Imager (SDI) instruments in Alaska and examine how both horizontal and vertical winds change during the geomagnetic activities. To assess the performance of our reconstruction method, we compared the horizontal wind with the ones derived from the monostatic fitting [Conde et al., 1998] and spherical elementary current systems [Amm et al., 2010]. In addition, we investigated the horizontal distribution of horizontal and vertical winds on October 28, 2016 when the Harang aurora activity is observed by Time History of Events and Macroscale Interactions during Substorms (THEMIS ) All Sky Imagers (ASI). The results of case study showed that the upward vertical winds became enhanced and the magnitude of vertical winds reached ~ 80 m/s during Harang aurora. Our results indicates that the vertical winds have more complicated features than earlier studies. Furthermore, the direction of horizontal winds shows the clockwise pattern around the Harang aurora and it turned to southeastward after the Harang structure was disappeared, which are also consistent with previous horizontal wind models.