## 3 Results and Analyses
From Figure 6, the EIA crests at both hemispheres are clearly variable during the storms, and the enhancements are very prominent in both hemispheres, immediately after the SSCs and the HSSW events, and followed by a significant variability in the main phases of the storms. The TEC enhancements in the low-latitude ionosphere on February 19 resulted from an increased merging electric field, E\({}_{\rm m}\). This results from the northward IMF B\({}_{\rm z}\) and an enhanced solar wind. Clear changes in the geomagnetic field of Earth (Figure 1i,j) are seen as the magnetosphere is compressed by the solar wind, and, for a particular orientation of IMF B\({}_{\rm z}\), the magnetospheric compression can be asymmetric if there is a significant IMF B\({}_{\rm z}\) component. This, in turn, is reflected in the merging electric field (E\({}_{\rm m}\)), and results in significant TEC enhancements. Figure 8 collects the results from  
Figure 5: Distribution of median average (**a**) IRI-2012 TEC and (**b**) IGS GNSS GIMs TEC during February 2014. Gray dashed line marks the geomagnetic dip equator. Red solid lines mark the profiles used to extract TEC near the EIA crests (approximately \(\pm 15^{\circ}\) to geomagnetic equator). The coordinates of the GNSS (marked with “x”) and geomagnetic (marked with “o”) stations are listed in Tables 1–3. previous figures and includes the merging electric field, E\({}_{\rm m}\), the geomagnetic SYM-H, Am, and Dst indices, the dPPEF, dEEJ, and rTEC variations measured by GNSS stations and magnetometers in Africa, and the GIMs TEC differences between the IGS products, as well as the quiet-time PCA-based model (Am = 6) at the EIA crests and at the magnetic equator. Colors are used to differentiate the GNSS stations in terms of proximity to the profiles, and the SSCs and HSSW are highlighted with vertical yellow and green lines, respectively. The overall variations are most prominent during the main phase of the storm caused by the HSSW event on 19 February, followed by a complex re-energization due to the SSCs on 20 and 23 February. In these events, there is an observation of the energization in the magnetosphere-ionosphere system due to an intensified ring current, which is clearly seen by the SYM-H index (Figure 8c). Immediately after the CME arrival on 19 February at \(\sim\)2 h UT, the TEC variability at the northern and southern EIA crest in Figure 8j shows very prominent enhancements of approximately 15 TECU, followed by a rapid drop to normality at the end of the day. Then, at \(\sim\)3:00 UT on 20 February, a new SSC enhanced EIA crest appeared again. In the northern EIA crest, the TEC enhancements reached \(\sim\)8 TECU, which lasted until the morning of 21 February, while the southern EIA crest dropped to normal values until midday of 20 February. Then, on 22 February, enhancements of \(\sim\)10 and \(\sim\)8 TECU appeared in the northern and the southern EIA crest, respectively, while no SSCs were observed during this period; only a small variation in Dst and AE indices was observed. Several hours after this point, on 23 February at \(\sim\)7 h UT, the SSC intensified both EIA crests by \(\sim\)8 TECU, with a slow recovery until 24 February at \(\sim\)12:00 UT. The TEC at the magnetic equator remained intensified at approximately \(\sim\)10 TECU from the beginning of the HSSW at \(\sim\)2:00 UT on 19 February until \(\sim\)12:00 UT on 24 February, with a  
Figure 6: Low latitude GIMs TEC differences between the IGS products and the PCA-based model set for quiet conditions (Am = 6). The differences are along the (**a**) southern and (**b**) northern EIA crests (\(\pm\)15\({}^{\circ}\)) and along (**c**) the magnetic equator, from 10 to 28 February 2014. The profiles used to extract TEC are shown in Figure 5a. The bottom panel (**d**) shows the mean values along the (**a–c**) profiles. The SSCs and the HSSW are highlighted with vertical yellow and green lines, respectively.