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Abstract
The effects of geomagnetic storms on ionospheric irregularities for radio communication are studied here using Global Positioning System (GPS) data recorded by the receiver at ABFC- station, Abuja (9.02767 °N, 7.48634 °E), Office of Surveyor General of the Federation, Nigeria. GPS Total Electron Content (TEC) and its rate of change index (ROTI) are utilized to show the effects of geomagnetic storms on the development of irregularities during the low solar activity year of 2021. Analysis of the Disturbance storm time (Dst) and ROTI indices indicate that most of the selected storms of the year are in agreement with Aarons (1991) criteria on the inhibition and generation of ionospheric irregularities in equatorial regions. Only a few storm events showed deviation from the Aarons’ hypothesis, and these were attributed to magnetosphere-ionosphere internal mechanism. However, cases of irregularities occurring during moderate and intense storm (Dst<-100) periods show clearly that the development of irregularities can be triggered or inhibited by geomagnetic storms during the period of low and high irregularity occurrence seasons, depending on the time of storm commencement, peak Dst excursion, recovery phase and local time. The effects (enhancements, inhibitions, or no effects) depend on the local time sector, and can be explained by the response of the equatorial plasma vertical drifts to magnetospheric and ionospheric disturbance electric fields.
