## 2 Experimental Facilities and Data
As receivers operate at ~1.6/1.2 GHz (L1/L2) at 100-300 km, the size of the irregularities primarily affecting the navigation signal amplitude is 100-300 m.  
(4) Additionally, we used the total electron content (TEC) variations obtained by using the dual frequency GPS/GLONASS phase measurement. The technique for the TEC calculation is well-known [38; 39; 40]. \[I=\frac{1}{40.308}\frac{f_{1}^{2}f_{2}^{2}}{f_{1}^{2}-f_{2}^{2}}[L_{1}\lambda_{ 1}-L_{2}\lambda_{2}+const+\sigma\varphi]\, \tag{3}\]  
where \(\mathbf{L_{1}}\)\(\mathbf{A_{1}}\) and \(\mathbf{L_{2}}\)\(\mathbf{A_{2}}\) are the radio signal carrier phase ranges including ionospheric delay (m), \(\mathbf{L_{1}}\) and \(\mathbf{L_{2}}\) are a number of phase rotations at \(\mathbf{f_{1}}\) and \(\mathbf{f_{2}}\) frequencies; \(\mathbf{\lambda_{1}}\) and \(\mathbf{\lambda_{2}}\) are corresponding wavelengths; \(const\) is an unknown initial phase ambiguity (m); and \(\sigma\varphi\) is a term corresponding to noise in phase measurements (m). By convention, 1 TEC Unit (TECU) = 10\({}^{16}\) electrons/m\({}^{2}\). We used the data from 5172 receivers of the global and regional GPS/GLONASS receiver networks (see Acknowledgments), including the IGS [41], UNAVCO, SONEL, etc., as well as the regional data, like SibNet [42], CHAIN [43], EUREF [44] HIVE ([[https://hive.geosystems.aero/](https://hive.geosystems.aero/)]([https://hive.geosystems.aero/](https://hive.geosystems.aero/))), etc. Blue dots in Figure 1 show the location of the used receivers. Single cycle slips in the TEC data were eliminated by the formula:  
\[\text{TEC(i)}=\text{TEC(-1)}+\text{TEC(i)}-\text{TEC(0)}+[\text{TEC(-1)}-\text {TEC(-2)}]/2+[\text{TEC(1)}-\text{TEC(0)}]/2. \tag{4}\]  
where \(i\) is the time instance after a cycle slip, TEC(0) is the TEC value, when the cycle slip is recorded, TEC(1) corresponds to TEC records after cycle slip, TEC(-2) and TEC(-1) correspond to two TEC records before the cycle slip occurred. We used an approximation that the time derivative equals the mean derivative before the cycle slip and after it. A similar approach was used to eliminate loss-of-lock effects. Variations in TEC within 15 min-3 h correspond to TIDs and other wave-like ionospheric disturbances. As TEC variations, we considered detrended and filtered TEC values. We performed the following procedure [45]. We detrended TEC data based on smoothing spline. After this, we used the running average with a 10-20 min (20-60 min) window to filter variations corresponding to medium-scale travelling ionospheric disturbances. Thus, we obtained the TEC variations series dI. We used a single layer model [46] as a mapping function to reduce TEC variations' dependence on the elevation angle. We mapped the variations on the globe given the ionospheric pierce point location and obtain the global spatial distribution of TEC variations [40]. We marked each ionospheric pierce point (at 300 km height) with the color corresponding to the TEC variation value. All calculations of TEC variations were performed by SIMuRG ([[https://simurg.iszf.irk.ru](https://simurg.iszf.irk.ru)]([https://simurg.iszf.irk.ru](https://simurg.iszf.irk.ru))) [47]. (5) To estimate the GPS precision, we calculated the station coordinates in the kinematic GPS dual-frequency precise point positioning (PPP) mode. For that purpose, we used the GAMP open-sourcesoftware [48]. Receiver and satellite clock offsets were considered in GAMP PPP solution by applying IGS precise satellite orbit and clock products. In addition, using linearized equations of original pseudorange and carrier phase observations, GAMP considers line-of-sight (LOS) ionospheric delay, receiver non-calibrated code delay, receiver and satellite non-calibrated phase delays, and zenith wet delay. We used a dual-frequency PPP model, in which the receiver non-calibrated code delays are absorbed by both receiver clock offset and LOS ionospheric delay parameters. The 24-hour median values of X, Y, Z coordinates for a station were regarded as reference positions.