TITLE:
Modeling of the TEC during Periods of Quiet Geomagnetic Activity at the Niamey GPS Station during Cycle 24
AUTHORS:
Wambi Emmanuel Sawadogo, Inza Gnanou, Moussa Sankara, Doua Allain Gnabahou, Boukar Makinta, Frédéric Ouattara
KEYWORDS:
Total Electron Content (TEC), Quiet Geomagnetic Activity, IRI-2020, NeQuick2
JOURNAL NAME:
Open Journal of Applied Sciences,
Vol.16 No.6,
June
15,
2026
ABSTRACT: The IRI-2020 model predicts the presence of intense counter-electrojet at the Niamey equatorial station during periods of quiet geomagnetic activity, across different solar cycle phases and seasons. Generally, Total Electron Content (TEC) variability exhibits a trough at dawn and a rapid increase after sunrise, reaching a peak in the afternoon. This is explained by the decrease in photoionization during the night and an increase in recombination. After sunrise, the intensification of solar radiation increases photoionization, causing a rapid increase in the TEC until the local afternoon peak. After sunset, the TEC decreases due to the reduction in photoionization and the strengthening of recombination. The IRI model indicates, as expected, that ionization increases with sunspot activity. Indeed, the TEC is maximal during the maximum phase and minimal during the minimum phase. Since the variation in the number of sunspots is positive during the ascending phase and negative during the descending phase, TEC values are higher during the ascending phase than during the descending phase. The seasonal variation of the TEC shows a semi-annual anomaly, meaning greater ionization at the equinoxes than at the solstices. Autumn values are higher than spring values, and winter values are higher than summer values. The IRI-2020 prediction indicates a nighttime winter anomaly from 2100 LT until dawn. The comparative study between the predictions of the NeQuick2 model and the reference IRI model shows considerable discrepancies during the day. However, at night, the two models present similar estimates.