Using Ionosonde Observations during Geomagnetic Storms for Studying Equatorial Ionospheric: Comparisons with IRI Model

For a study of variations of the equatorial ionosphere, ionosonde observations of F2-peak electron density (NmF2) from equatorial stations during geomagnetic storm events have been used. The data used covered stations in the regions of equatorial ionization anomaly (EIA). The diurnal and seasonal variations of NmF2 are analyzed and the results were used to validate the predictability of IRI 2016 model predictions during geomagnetic storms. In general the results showed that IRI model predictions reveal more or less a similar diurnal trend of observation values. However, major discrepancies were observed during some storm events when the IRI either underestimates or overestimates observed values, where the percentage deviation of the observed values with respect to IRI varies from 15 to about 120%. Details of the statistical analysis of the results and the accuracy of the IRI model predictions are discussed.