This paper presents for the first time results on winds, tides, gradients of horizontal winds, and momentum fluxes at mesosphere and lower thermosphere (MLT) altitudes over southern Patagonia, one of the most dynamically active regions in the world. For this purpose, measurements provided by SIMONe Argentina are investigated. SIMONe Argentina is a novel multistatic specular meteor radar system that implements a SIMONe (Spread Spectrum Interferometric Multistatic meteor radar Observing Network) approach, and that has been operating since the end of September 2019. Average counts of more than 30000 meteor detections per day result in tidal estimates with statistical uncertainties of less than 1 m/s. Thanks to the multistatic configuration, horizontal and vertical gradients of the horizontal winds are obtained, as well as vertical winds free from horizontal divergence contamination. The vertical gradients of both zonal and meridional winds exhibit strong tidal signatures. Mean momentum fluxes are estimated after removing the effects of mean winds using a four-hour, eight-kilometer window in time and altitude, respectively. Reasonable statistical uncertainties of the momentum fluxes are obtained after applying a 28-day averaging. Therefore, the momentum flux estimates presented in this paper represent monthly mean values of waves with periods of four hours or less, vertical wavelengths shorter than eight kilometers, and horizontal scales less than 400 km.

The study of the mesosphere and lower thermosphere (MLT) dynamics presents great challenges. One of them is trying to find a dominant theory that explains mesoscales variations. Recently, Vierinen et al. (2019) introduced the Wind field Correlation Function Inversion (WCFI) technique that estimates spatial correlation functions (among other products) of the wind velocity field in the MLT from multistatic specular meteor radar observations. The correlations can be determined for lags in two dimensions (East-West and North-South directions), from which the frequently used hypothesis of horizontal isotropy on correlation functions of the fluctuating wind can be examined. Moreover, using the two dimensional correlation functions of the fluctuating wind, we investigate the two-point correlations of vertical vorticity (Qzz) and horizontal divergence (P) (Lindborg, 2007). Assuming that the velocity field is statistically homogeneous in horizontal planes of certain thickness, these functions can be expanded to get similar, compact forms. Qzz and P are of great significance since they can provide information on the relative importance of stratified turbulence and internal gravity waves to explain the mesoscale dynamics in the middle atmosphere.