The performance of the IRI-Plas model as compared with Alouette II and GIM-TEC data over the midlatitude station Alma-Ata

Abstract

Climatic ionospheric models present an important medium for both investigation of physical structure and correction of detrimental effects of ionospheric variability on space based communication, navigation and positioning systems. International Reference Ionosphere Extended to Plasmasphere (IRI-Plas) is one of the empirical models that can provide ionospheric layer parameters and electron density profiles up to GPS satellite orbital height of 20,200 km. IRI-Plas can input not only F2 layer critical parameters, foF2 and hmF2, but also the Total Electron Content (TEC) values. In this study, Ne(h)-profiles and TEC values obtained from the IRI-Plas model are compared with topside Alouette II satellite profiles and Global Ionospheric Map (GIM) TEC values, respectively. The satellite Ne(h) profiles are averaged over a midlatitude region for various seasons of 1966 and 1969. It is observed that IRI-Plas is in good agreement with Alouette profiles between 300 km and 500 km. After 500 km up to 2000 km, the profiles seem to differ where IRI-Plas Ne(h) usually overestimates the Alouette profile. When IRI-Plas TEC is compared with GIM-TEC, it is observed that model TEC generally overestimates the GIM-TEC values during daytime hours. The lowest ΔTEC values (10–20%) are observed in March and September, and the highest values are observed in the months of January (around 30%) and July (up to 67%). During nighttime, the IRI-Plas model results mainly underestimate the observational ones, up to 30% in equinoctial months, and with ±10% discrepancies in January and July. Since the IRI-Plas model can scale foF2 and hmF2 values using an external TEC input by equating instantaneous and median slab thickness (TEC/NmF2 ratio), the correlation between GIM-TEC and ionosonde NmF2 values measured at the midlatitude station Alma-Ata located at [43.25°N, 76.92°E] is obtained for various seasons during 1999, 2000, 2008, 2009 and 2012. The study showed a positive correlation for all seasons and levels of solar activity. The correlation coefficients between the data sets were very high (greater than or equal to 0.79) for hourly data and (greater than or equal to 0.91) for monthly-medians at a significance level of 5%. Thus, for the practical applications, the correlation results can be used to update slab thickness model of IRI-Plas which will lead to better scaling of foF2 and hmF2 values and plasmaspheric Ne(h)-profile with external instantaneous TEC input.