We investigated the American low-latitude ionosphere around 75°W during the two 2013 sudden stratospheric warming (SSW) events: one in quiet geomagnetic conditions, and the other overlapped by a minor geomagnetic storm using total electron content (TEC) data from 12 Global Positioning System (GPS) receivers. A pair of magnetometers revealing the varying inferred vertical E X B drift and the NASA Thermosphere Ionosphere Mesosphere Energetics and Dynamics (TIMED) satellite airglow instrument to understand the global changes in the neutral composition, O⁄N_2 ratio are also used. The late morning inferred downward-directed E X B drift during the first major SSW did not support the varying equatorial ionization anomaly (EIA) signature. However, during the second major SSW, the well-reported and enhanced late morning inferred upward-directed E X B drift relocated a northern EIA crest to higher latitudes. Interestingly, the effect of a minor geomagnetic storm on 17 January 2013 that modulated the ongoing second SSW reduced the maximum inferred upward-directed E X B drift. The second major SSW contribution to the northern crest is higher than photo-ionization and the first major SSW contribution, while each major contribution is higher than minor warming. The minor geomagnetic storm reduced the effect of the second major SSW on the TEC from 58% to 50% and 28% to 20% at the northern and southern crest, respectively. Also, the storm’s overall effect of - 1 % (22 %) leads to a slight reduction (enhancement) in TEC magnitude at the northern (southern) crest.

This paper examined the variability of equatorial thermospheric meridional and zonal wind speeds at night-time using an optical Fabry–Perot interferometer (FPI) located in Abuja, Nigeria (Geographic: 8.99°N, 7.39°E; Geomagnetic latitude: -1.60). The study period covered 9 months with useable data of 139 nights between March 2016 and January 2018. The hourly zonal wind speed is between 19.33 and 250 ms-1 and that of the meridional wind ranged between 0 and 200 ms-1. These speeds are greater than those reported in other longitudinal sectors, and this could be one of the reasons responsible for reduced EXB drift in this region compared to other regions. Comparison of FPI ground-based measurements with estimates from the Horizontal Wind Model (HWM-14) accurately reproduced the meridional component, but for some departure of ~45 ms-1 in May and June 2016, and January 2018. A very good agreement is observed between the predicted and measured zonal winds speed in the months of 2017. However, the HWM-14 overestimated the zonal wind speed in the early evening values by ~30 ms-1 and underestimated the post-midnight values by a larger factor in December 2017. Hence, this necessitates a call for improvement of the HWM-14 by using newly observed data in order to better characterize the West African sector. The varying zonal winds showed modal periods of 25.9 and 133.5 days, which are quasi 27-days and quasi-terannual periodic variations, respectively. On the meridional wind, oscillatory periods of 133.5 and 23.1 days are seen in year 2016 and 2017, respectively.