Evaluations of two ion temperature models in IRI-2020 based on the observations from ICON and COSMIC-2 IVM

Abstract

Ion temperature is a critical parameter for understanding the ionospheric thermal processes. Its measurement is relatively sparse compared to other ionospheric parameters, and validation of existing empirical models remains an important task. This study deals with the quiet time low- and mid-latitude topside ionospheric ion temperature measured by the Ionospheric Connection Explorer (ICON) and the Constellation Observing System for Meteorology Ionosphere and Climate (COSMIC-2). We conducted statistical analysis for local time, latitudinal, seasonal and solar activity variations. The comparison of the observations with two ion temperature models (Bil-1981 and TBKST-2021) of the International Reference Ionosphere-2020 (IRI-2020) shows that TBKST-2021 performs better than Bil-1981. TBKST-2021 model captures the morning and afternoon peaks quite well although with some underestimation. The underestimation of the morning and afternoon peaks may be due to overcorrection. Further, it shows a good seasonal and latitudinal dependence, with a better performance at the equinox than in solstices. However, TBKST-2021 requires to improve the presentation of hemispheric differences in solstices.