Relation of internal gravity wave anisotropy with neutral wind characteristics in the upper atmosphere

AbstractThis paper studies the interaction of internal gravity waves (IGW) with neutral wind using the statistics of traveling ionospheric disturbances (TID) from the Radio Physical Complex of the Institute of Solar‐Terrestrial Physics. The complex includes the Irkutsk Incoherent Scatter Radar (IISR), Irkutsk Ionosonde (DPS‐4), and Ekaterinburg HF Radar (EKB). The aim of this study is to give a common explanation for the TID azimuth distributions obtained with the IISR‐ionosonde and HF coherent radar and show that the measurements of 3‐D TID characteristics put into the hands of researchers an important tool to study neutral wind in the thermosphere. The distinctive features of this study are the following: (1) using different TID statistics from independent tools and, correspondingly, independent methods for determining TID characteristics; (2) using the 3‐D TID characteristics for testing the wind‐filtering hypothesis, which allows us to separate the IGW‐induced TIDs from TIDs of other nature and identify three TID types depending on their elevation angles; and (3) using the local time‐azimuth distribution of the TID number for testing the wind‐filtering hypothesis. This study allowed us to conclude that the observed IGW azimuth anisotropy can be mainly explained by the wind filtration mechanism with considering winds at 90–250 km heights. Using the 3‐D IGW characteristics allows us to estimate neutral wind parameters. Proposed methods are applicable for any tool which can obtain TID 3‐D characteristics. Using the proposed methods will enable us to organize a worldwide campaign to improve the existing neutral wind models.