## 5 Conclusions  
In February 2014, the Sun produced eleven small halo CMEs, including four powerful Earth-directed CMEs that triggered a multiphase geomagnetic storm. The first CME (generated two M-class flares on 12 February) arrived to Earth on 15 February and caused a minor geomagnetic storm. On 19 February, the prevalent minor G-1 geomagnetic storm was still in the recovery phase when a sudden HSSW event reenergized the existing disturbances, causing a complex moderate G-2 geomagnetic storm. Two more SSC events on 20 and 23 February 2014 made the storm highly complex. In this work, the low-latitude ionosphere responses and coupling mechanisms of this complex multiphase geomagnetic storm are investigated using space weather indices, magnetometers, and TEC data from ground-based GNSS stations, and ionospheric empirical models. The main conclusions from our analyses are as follows:  
* Clear TEC depletions/enhancements were observed at the GNSS stations used in this study, and TEC enhancements from the IGS GIMs are up to 20 TECU, lasting from 16 to 18 February 2014. A delay in TEC enhancements towards high-latitude stations was observed, which is attributed to the EIA expansion. TEC enhancements up to 20 TECU have been at low-latitudes with longer-lasting TEC enhancements at the dip equator (from 16 to 18 February) rather than in the EIA crests (only after the CMEs arrivals). * Rapidly after the arrival of each CME, PPEF disturbances with amplitudes of 0.4 mV/m have been observed in the American, African, and Asian sectors. The EEJ variations exceeded amplitudes of 100 nT with the exception of the Asian region, which has shown minimal EEJ variability. * The HSSW event on 19 February seems to have reenergized the existing storm conditions (CME arrival of 15 February) and subsequently caused a moderate G-2 geomagnetic storm, which was further enhanced by two more SSC events on 20 and 23 February. The prevalent magnetospheric convection caused by the preceding southward IMF on 19 February was the cause of no classical SSC. From the HSSW event, there has been the observation of a gradual increase in GEC up to 3.5 GECU at the end of the month, showing approximately 1 GECU of differential intensification. This gradient is not reflected by the IGS-derived TEC profiles, but clear rTEC enhancements over 60% during the same period at the RABT GNSS ground station were noticed, suggesting this enhanced TEC to be located at higher latitudes. * The IRI-2012 model did not represent the actual TEC variability during the storms period, showing no distinction between events, and a clear bias of \(\sim\)20 TECU to the actual quiet-time TEC. There was also a detection of a clear discrepancy in the distribution of TEC along the EIA, showing that IRI-2012 underestimates the northern crest at the African and Asian sectors and at both crests in the American sector. The median February average from the IGS GIM TEC shows enhanced values in the southern hemisphere, whereas the IRI-2012 does not show this asymmetry. **Author Contributions:** Investigation, data curation, visualization, writing--original draft preparation, A.C., C.A., M.S., Y.Y. and C.O. ; conceptualization, formal analysis, supervision, writing--review and editing, A.C., C.A.-M. and S.J. ; funding acquisition, S.J. All authors have read and agreed to the published version of the manuscript. **Funding:** This research was partly funded by: (S.J.) the National Natural Science Foundation of China (NSFC) Project (Grant No. 12073012), Nanjing, China; (A.C.) the Talent Start-Up Funding project of NUIST (Grant No. 1411041901010), Nanjing, China; (A.C.) the Giner de los Rios Grant of University of Alcala, Madrid, Spain; and (Y.Y.) the Ministry of Science and Higher Education of the Russian Federation, Irkutsk, Russia. **Institutional Review Board Statement:** Not applicable. **Informed Consent Statement:** Not applicable. **Data Availability Statement:** Not applicable.