An overview of IRI-observational data comparison in American (Brazilian) sector low latitude ionosphere

This paper presents an overview of the existing results of comparisons between the IRI-90 predictions and the observational data for the Brazilian longitude sector and attempts to place the major findings in a global perspective. The observational data subjected to comparison with the IRI model include NmF2/foF2 (the peak density/critical frequency of the F2-layer), hmF2/ hpF2 (the height of NmF2/foF2), TEC (total ionospheric electron content) and the electron density-height profiles. The Brazilian stations for which results are presented are: Fortaleza near the magnetic equator and Cachoeira Paulista near the equatorial anomaly crest. The results are compared with those from Asian and Indian longitude sectors. An attempt is made to identify points of agreement/disagreement between the observational data and the IRI. Seasonal and solar activity dependent persistent trends of discrepancies have been found with respect the NmF2, hmF2 and TEC. We have tried to highlight the global nature of such discrepancies aiming at providing an eventual basis for incorporating needed modification for improving the predictive capability of the IRI for the equatorial and low latitude ionosphere.