A comparison of a model using the FORMOSAT-3/COSMIC data with the IRI model

Abstract

In this study, an empirical model constructed using data of FORMOSAT3/COSMIC (F3/C) from 29 June, 2006, to 17 October, 2009, retrieves altitude profiles of electron density (N e ). The model derives global N e profiles from 150 to 590 km altitude as functions of the solar EUV flux, day of year, local time and location under geomagnetically quiet conditions (K p < 4). N e profiles derived by the model are further compared with those of the International Reference Ionosphere (IRI). Results show that the F 2 peak altitude h m F 2 and the electron density N m F 2 , as well as the electron density above, derived by the model are lower than those of the IRI model. The F3/C model reproduces observations of F3/C well at 410-km altitude while the IRI model overestimates them. The overestimation of the IRI model becomes large with decrease of EUV flux. It is found that the topside vertical scale height of the F3/C model shows high values not only magnetic dip equator but also middle latitude. The results differ significantly from those of IRI, but agree with those observed by topside sounders, Alouette and ISIS satellites.

Impacts of solar activity on performance of the IRI-2012 model predictions from low to mid latitudes

“…This approach has the disadvantage of discrepancies between the experimental and model TEC values during high solar activity years (Mukherjee et al 2010). The IRI-2007 was released with many enhanced features and showed a good agreement with the observed data at the anomaly crest station (Chauhan and Singh 2010 IRI-2001, and IRI01-corr) at different equatorial and low-latitude regions (Watthanasangmechai et al 2012;Wichaipanich et al 2012;Kakinami et al 2012;Okoh et al 2012;Oyekola 2012;Oyekola andFagundes 2012a, 2012b).…”

TEC prediction performance of the IRI-2012 model over Ethiopia during the rising phase of solar cycle 24 (2009–2011)

“…2, 3, and 4. The VTEC overestimation could also be due to a decrease of the flux of extreme ultraviolet (EUV) radiation (Kakinami et al 2012). As shown in Figs.…”

“…Hence, the authors conclude that the sunspot number (Rz12) is not a good index to describe ionospheric conditions during the solar minimum, particularly for the recent solar minimum, and they recommend using the ionospheric index (IG12) for the hmF2 model instead. Furthermore, Kakinami et al (2012) describe that the overestimation of the TEC by the IRI model increases with a decrease of EUV irradiance (during low solar activity) and decreases with an increase of EUV (during high solar activity). As shown in Figs According to Johnson (1963), Torr and Torr (1973), and Rishbeth and Setty (1961), the lowest VTEC observed during the June solstice is possibly due to the asymmetric heating of the two hemispheres, which results in transportation of neutral constituents from the summer to the winter hemisphere, thereby reducing the recombination rate (or lose of electrons).…”

“…In addition, the model performance in estimating diurnal VTEC variations was found to be better during low solar activity phases than during high solar activity phases. Abdu et al (1996), Kakinami et al (2012), Kumar et al (2015), andMcNamara (1985) attempted to describe the model's capacity to estimate the TEC in low-and mid-latitude regions. However, so far nobody has conducted a study to investigate patterns of VTEC variation over Ethiopian regions during the rising phase of solar cycle 24.…”

Validation of the IRI-2012 model with GPS-based ground observation over a low-latitude Singapore station

“…From these results, the IRI-2012 model-based profile is normally found to be in agreement with COSMIC measurements around 250-to 300-km altitudes. Recently, Kakinami et al (2012) has compared COSMIC-based electron density profiles with those estimated with the IRI-2007 model and showed that the COSMIC-based electron density profile at and above F2 peak altitude is lower than that estimated by the IRI model. For a detailed comparison between the COSMIC and IRI-2012 model profiles, the percentage deviation in the electron density as compared to COSMIC RO measurements at lower (200 km), peak (hmF2), and topside (600 km) altitudes has been calculated and are listed in Table 1.…”