Diurnal variations of the horizontal component of the geomagnetic field ΔH on International Quiet days of 1999–2012, measured hourly at two stations in the same longitude zone in the Northern Hemisphere, near and away from the dip equator, have been subjected to principal component analysis. This technique is also applied to the difference ΔHEEJ of ΔH at these two stations, which is attributed to the equatorial electrojet (EEJ). The first three principal components, PC1–PC3, account for 91–96% of the variances in the data. Maximum contribution to the quiet day variations in ΔH around its peak in the morning hours at both the stations, and in the EEJ, comes from the day‐to‐day variation of the amplitude of PC1. Patterns of day‐to‐day variations of PC1 amplitudes for the equatorial station and the EEJ are essentially semiannual modulated by solar EUV flux, superimposed on a longer timescale solar EUV flux‐dependent trend. Contributions from PC2 and to a lesser extent from PC3 are seen to be responsible for the absence of semiannual variations in ΔH in the afternoon hours at the equatorial station. Distribution of amplitudes of PC2 and PC3 for ΔHEEJ for weak electrojet days shows seasonal features in accordance with greater occurrence of afternoon (morning) counter electrojet during June (December) solstice. During the extended solar minimum, PC3 amplitudes for ΔH at the equatorial station and for the EEJ display annual variation. Possible sources for these seasonal features in the variations of equatorial ΔH are discussed.

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Changes in vertical total electron content (VTEC) over West Africa which were associated with four geomagnetic storms in 2015 have been studied. The spatial evolution of the quiet time TEC over West Africa for four months (vis; March, June, October and December) which may give rise to unique features of the storm TEC were also evaluated. Quiet-time VTEC (i.e Sq VTEC) was obtained using the hourly means of the international quietest days for each month when a storm of interest occurred. The change in TEC ( ) was obtained after removing the quiet time VTEC from the storm day VTEC.  A significant latitudinal variation in VTEC was observed at 22:00LT over West Africa and this was accompanied by the usual broad peak at about 14-17UT. The latitudinal disparity observed in the Sq  at 22.00LT was likely driven by the intesification of the fountain effect. The maximum   observed during the storms in 2015 were of the other of 16 TECU. These results have important implications for our present understanding of TEC evolution during a geomagnetic and its direct effect on the technologies that depend on it.

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Galactic cosmic rays are modulated in the heliosphere primarily by the global merged interaction regions with intense magnetic fields, which leads to a decrease in galactic cosmic rays throughout the heliosphere. Using long-term averages of solar wind (SW) component parameters in addition to cosmic ray count rates of four neutron monitors with different rigidity cutoffs, we analyzed the effect of these SW components on the count rates under different interplanetary magnetic field (IMF) disturbance levels. From first-order partial correlation, we found that the IMF-B was the most dominant modulating parameter, especially during quiet conditions and the SW dynamic pressure was more effective during disturbed conditions. The influence of more subtle parameters like wind speed, Bz component, and proton density were masked by these dominant parameters: IMF total B, and SW dynamic pressure.