## 2 Materials and Methods
### Estimation of the Ionospheric Total Electron Content  
The inherent space-time variability of the ionosphere can be observed through TEC that can be obtained using GNSS stations [32]. Then, GNSS measurements based on dual-frequency signals \(f_{1}\) and \(f_{2}\), were used to obtain the vertical TEC (VTEC) data. The ground-based dual-frequency GNSS (DF-GNSS) receiver continually records two types of delay: the pseudoranges and the carrier phases of the two signals. The obtained data was used to estimate the slant TEC (STEC) and to calculate the VTEC. STEC and VTEC were calculated from Receiver Independent Exchange Format (RINEX) files by using the GPS-TEC analysis software (GPS-TEC program Ver 2.9.5, developed by Dr. [PERSON], https://seemala. blogspot.com/2017/09/gps-tec-program-ver-295.html, last accessed on 17 April 2022) [24]. VTEC values were estimated with a satellite cut-off elevation angle of 30\({}^{\circ}\) at an altitude of 350 km to reduce possible errors. The TEC values were released every 30 s and were corrected for the satellite and receiver bias using the data obtained from the AIUB Data Center of Bern University in Switzerland ([[ftp://ftp.aiub.unibe.ch/CODE/](ftp://ftp.aiub.unibe.ch/CODE/)]([ftp://ftp.aiub.unibe.ch/CODE/](ftp://ftp.aiub.unibe.ch/CODE/)), last accessed on 17 January 2022). For the final selection of the RINEX files of each GNSS station, we took into account several aspects. First, we considered the quality of the files during the selected period of days (DoYs 159-163). Second, we verified that there were no errors or data-gap after TEC estimation and post-processing PPP-AR. This aspect is critical to relating TEC and/or ROTI with positioning variations. We used data from all available stations in the polar regions. We also tried to cover regions such as Africa, Australia, and Asia. The International GNSS Service (IGS) stations ([[http://www.igs.org](http://www.igs.org)]([http://www.igs.org](http://www.igs.org)), last accessed on 17 January 2022) [33]; the Chilean network of GNSS receivers operated by the National Seismological Center at University of Chile (CSN in Spanish); University NAVSTAR Consortium (UNAVCO); the Argentine Continuous Satellite Monitoring Network (RAMSAC in Spanish) [34]; the Brazilian Network for Continuous Monitoring of the Institute of Brazilian Geography and Statistics (IBGE in Portuguese); the Geoscience Australia; the Low-Latitude Ionospheric Sensor Network (LISN, [[http://lisn.igp.gob.pe/](http://lisn.igp.gob.pe/)]([http://lisn.igp.gob.pe/](http://lisn.igp.gob.pe/)), accessed on 26 July 2021); and the African Geodetic Reference Frame (AFREF) provided RINEX files of 2337 GNSS stations that met the requirements we imposed (see Figure 1). Additionally, the differential VTEC (DVTEC) in TECu and the percentage changes of DVTEC (DVTEC[\(\%\)]) were used. These parameters are studied in the analysis of ionospheric irregularities, defined as the relative variation of VTEC, epoch by epoch, with respect to the mean value (in time) of \(\overline{VTEC}\) as shown in Equations (1) and (2) [35]. \[DVTEC_{t}=VTEC_{t}-\overline{VTEC_{t}} \tag{1}\]  
\[DVTEC[\%]_{t}=\frac{DVTEC_{t}}{\overline{VTEC_{t}}}\cdot 100 \tag{2}\]  
where \(t\) represents the epoch, and \(\overline{VTEC_{t}}\) is calculated by averaging the values of VTEC at the same time of the day, \(t\), for the reference DoYs 159, 160, 162 and 163 which correspond to 2 days before and 2 days after the day of the eclipse (DoY 161). According to the methodology [29], we used the ordinary Kriging interpolation method to produce the TEC maps at each ionospheric pierce point (IPP). With this method, we filled in the spatial gaps of the global ionosphere TEC maps, minimizing the effects of the inhomogeneous distribution of GNSS receivers. Before interpolating, we selected a spatial resolution of 2.5\({}^{\circ}\)\(\times\) 2.5\({}^{\circ}\).