Comparisons of IRI model and electron density data for the sub-equatorial station, Natal

Database from CADI (Canadian Digital Ionosonde) recorded at Natal (5.2° S, 36° W) near solar maximum are used to compare with the International Reference Ionosphere (IRI) predictions. Such comparison is done using vertical profiles of electron density and F region peak parameters, the maximum electron density (NmF2) and its corresponding height (HmF2), for geomagnetically quiet and disturbed conditions. The mean behavior of the observed vertical electron density profiles at 0300, 0900, 1500 and 2100 UT (UT = LT + 2.4 hr) for quiet and disturbed periods was compared with IRI profiles. Generally, good agreement between the two sets is noted, but IRI underestimates the heights of the bottomside F region at 0900 and 2100 UT. Also, discrepancies are found between the observed values of NmF2 and HmF2 and those obtained from IRI using URSI coefficients during evening-nighttime period.