Longitudinal Asymmetry of the Occurrence of the Plasma Irregularities over African Low-Latitude Region

This study presents the results of plasma irregularities over African equatorial and low-latitude region under various solar-geophysical conditions that gave rise to an east-west longitudinal asymmetry. The data used for this research were obtained from the ground-based GNSS receiver stations within African equatorial ionization anomaly region, for 3 consecutive years (2011-2013) in the ascending phase of solar cycle 24. The study considered specific days of different geomagnetic activities in equinoctial month of October 2013. In addition, the five most geomagnetically disturbed and quietest days in each month for the 3 consecutive years and the annual mean for each year were considered in this study. Rate of change of total electron content index (ROTI) was used to access the level of the ionospheric irregularities activity. The presence of ionospheric irregularities was taken when the difference between the local daytime (0600-1800) and nighttime (1900-2400) mean ROTI is above 0.075 TECu/min. The study revealed that African equatorial ionospheric irregularities' occurrence is larger in the west sector and that irregularities activity could be sometimes 4-40% lowered or inhibited during the disturbed conditions in the African equatorial eastern sector in comparison to the western region. The asymmetry observed in the region could be attributed to transequatorial meridional winds and probably the east-west asymmetry in the strength of the EEJ current in the region.