This 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.

This study presents a new method for determining a neutral wind velocity vector. The basis of the method is measurement of the group velocities of internal gravity waves. Using the case of the Boussinesq dispersion relation, we demonstrated the ability to measure a neutral wind velocity vector using the group velocity and wave vector data. An algorithm for obtaining the group velocity vector from the wave vector spectrum is proposed. The new method was tested by comparing the obtained winter wind pattern with wind data from other sources. Testing the new method showed that it is in quantitative agreement with the Fabry–Pérot interferometer wind measurements for zonal and vertical wind velocities. The differences in meridional wind velocities are also discussed here. Of particular interest were the results related to the measurement of vertical wind velocities. We demonstrated that two independent methods gave the presence of vertical wind velocities with amplitude of ~20 m/s. Estimation of vertical wind contribution to plasma drift velocity indicated the importance of vertical wind measurements and the need to take them into account in physical and empirical models of the ionosphere and thermosphere.

Using the representative statistics on traveling ionospheric disturbances (TIDs) obtained by Yekaterinburg and Magadan radars, we have shown that distributions of TIDs and average TID velocities by azimuths and local time agree well with the hypothesis on internal gravity wave (IGW) filtering by the neutral wind. We have examined the influence of significant winter sudden stratospheric warmings on IGW in the ionosphere. A method has been proposed for estimating zonal and meridional neutral wind velocities from MSTID parameters. The method is universal and allows us to estimate the zonal and meridional neutral wind velocities from the statistics on MSTID 2D phase velocity vector obtained by any tool. There is a large amount of data from which MSTID 2D phase velocity vector (as opposed to the 3D phase velocity vector) can be derived, including maps of TEC disturbances and all-sky camera images. This method may therefore be useful in developing and improving neutral wind models.

Our paper presents the results of investigating wave structures detected in 630 nm atomic oxygen emission intensity (airglow height is ~180–300 km). The study employs data from a wide-angle optical system installed at the Geophysical Observatory of the ISTP SB RAS (51°48′ N, 103°04′ E). It describes the algorithm to identify wave disturbances and determine their main parameters in the optical system images. The results obtained due to automatic processing of 2014–2021 data archives are presented. The most probable values of the wave disturbances propagation velocity are about 80 m/s. The horizontal wavelengths and periods are in the range of ~30–400 km and 60–120 min, respectively. The predominant direction of disturbances propagation is to the southwest. The received data of optical and radio observations are compared. We found both similarities and differences in the wavelike structures direction, which are to be investigated in the future.