Comparison between IRI predictions and digisonde measurements at low latitude station

Abstract

The Digisonde database from Cachoeira Paulista (22.5° S, 45° W) is used to compare the observations with the IRI predictions. The data were registered during some periods from 1990 to 1993. The comparison is made for the F region parameters NmF2 and hmF2 and for true height profiles as well. The analysis, based on the quietest days during the data period, shows that while IRI provides realistic profiles during daytime hours of high solar activity periods, it seems to underestimate the bottomside electron density during the early morning and late afternoon hours. The F-layer peak density obtained using the CCIR-89 coefficients are underestimated for most of the nighttime hours during equinox and summer months of high solar activity periods, and are overestimated for most of the time during low solar activity.