Comparative statistical study of mid-latitude MSTIDs over two latitudinal regions using dense GNSS network

This work is devoted to potential sources and mechanisms of the mid-latitude MSTIDs formation based on the analysis and comparison of statistical data in two regions: 1 region near Samara (~ 55 N. 50 E), 2 region near Sevastopol (~ 45 N, 35 E). The data obtained using a dense GNSS receivers network (> 150 pcs.) in the European part of the Russian Federation. The study was carried out using a new statistical method for determining the vertical slopes of the MSTIDs phase front. It was found that summer nighttime MSTIDs over the region near Samara (~ 55 N, 50 E) have the traditional southwest directions of propagation and sloping forward phase fronts, while near Sevastopol (~ 45 N, 35 E) northwest directions with sloping backward phase fronts. We suggest that the influence of Mid-latitude Summer Nighttime Anomaly may be a trigger for the northwestward MSTIDs, as unlike the southwestern MSTIDs, they are observed 10 degrees south and only in the summer months and September. We do not propose the exact mechanism of their formation in this article, however, we note that sloping backward phase fronts of MSTIDs couldn't be form by the GWs with sources in troposphere. The propagation directions of the southwestward MSTIDs near Samara (~ 55 N, 50 E) are consistent with those that are expected for the growth of Perkins instability.