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.