Assessment of IRI-2012 profile parameters by comparison with the ones inferred using NeQuick2, ionosonde and FORMOSAT-1 data during the high solar activity over Brazilian equatorial and low latitude sector

The equatorial and low latitude ionosphere exhibits large variability in the electron density distribution. This variability is manifested by a typical dynamical phenomenon namely, the Equatorial Ionization Anomaly (EIA). In the presence of significant variabilities, accurate estimation of ionospheric Total Electron Content (TEC) has gained more importance in view of the communication and navigation applications. In the present study, the ionospheric electron density as well as the profile thickness and shape parameters of the latest available IRI (IRI-2012) and NeQuick (NeQuick2) models over the equatorial and low latitude sectors have been compared with experimental values for understanding their performance. The ground based ionosonde data in conjunction with the FORMOSAT-1(formerly called ROCSAT) measured in-situ electron density in the topside ionosphere have been used to derive the vertical electron density profiles over three identified locations in the Brazilian equatorial and low latitude sectors during the high solar activity year of 2002. Profiles reconstructed from the combination of ionosonde and FORMOSAT-1 data are compared with profiles derived from both IRI-2012 and NeQuick2 models. The diurnal and seasonal variations of TEC, F-layer peak density (NmF2), F-layer peak height (hmF2), bottom side thickness parameter (B0), shape parameter (B1) and topside effective scale height (HT) have been studied to validate the IRI-2012 and NeQuick2 model simulations. It has been noticed that these models underestimate the experimental TEC during day-time hours of the equinoctial and summer months of the high solar activity. The models perform better in the prediction of NmF2 and hmF2 than in the prediction of TEC during day-time hours. Further, it is observed that both IRI-2012 and the NeQuick2 models show considerable deviations in the estimation of the bottom side profile parameters while more discrepancies are observed in the prediction of topside effective scale height values particularly during day-time hours.