Predicted and measured electron density at 600 km altitude in the South American peak of the equatorial anomaly

Study of Ionospheric TEC from GPS observations and comparisons with IRI and SPIM model predictions in the low latitude anomaly Indian subcontinental region

“…Also, Shastri et al (1996) and Ezquer et al (2004) have shown that the prediction accuracy varies with local time and location, over low latitudes the model overestimates during hours of minimum TEC and underestimates during peak hours. From the experiments over 600 km above South American anomaly crest region, Ezquer et al (1999) conformed that IRI underestimates the observed electron density by 50% and 60% during equinox and winter, and overestimates by as much as 150% in summer. Also Bhuyan et al (2003) reported that IRI failsfailure of the IRI model to produce the secondary peak of electron density during the low solar activity period (1994)(1995)(1996)(1997).…”

“…The IRI is an empirical standard model sponsored by the Committee on Space Research (COSPAR) and the International Union of Radio Science (URSI) (Bilitza et al, 1990). Several papers have been published on the simultaneous measurement of foF2/TEC, its noontime bite-out and secondary peak during evening, winter anomaly, solar activity dependance, and corresponding model predictions in the equatorial and low latitudes (Sethia et al, 1979;Dabas et al, 1984;McNamara, 1985;Rastogi and Klobuchar, 1990;Batista et al, 1994;Abdu et al, 1996;Ezquer et al, 1999;Sethi et al, 2001Sethi et al, , 2011Rao et al, 2006;Bhuyan and Borah, 2007;Bagiya et al, 2009;Chauhan and Singh, 2010;Aggarwal, 2011;Adewale et al, 2012;Prasad et al, 2012;Olwendo et al, 2012;Bhuyan and Hazarika, 2013;Sur and Paul, 2013;Hazarika and Bhuyan, 2014;Kumar et al, 2014a). Efforts are also being made to update and improve the model since its development in 1969, with newer data and better modeling techniques.…”

Diurnal, seasonal and latitudinal variations of ion temperature measured by the SROSS C2 satellite in the Indian zone equatorial and low latitude ionosphere and comparison with the IRI

“…At low latitudes, the IRI was found to underestimate the observed TEC. Many other reports of comparison of IRI with foF2, TEC or topside density has since appeared in the literature (Ezquer et al, 1995(Ezquer et al, , 1999Abdu et al, 1996;Bilitza and Fig. 10.…”

“…They found that the model underestimates the observed electron density in all seasons and at about all local times during moderate and high solar activity. Ezquer et al (1999) have compared the electron density obtained by the Hinotori satellite at 15 • S geomagnetic latitude within the longitude zone 285 • -360 • . They found that the IRI predictions compare well with observation during hours of minimum (02:00 -08:00 LT) ionization in equinox and December solstice but strongly disagree during hours of maximum ionization ( ∼ 15:00 LT).…”

Critical frequency and maximum electron density of F2 region over four stations in the North American sector

“…The model takes into account daily and seasonal variations, perturbed and quiet conditions as well as the impact of solar activity on ionospheric conditions. The scientific community did several efforts to test the validity of ionospheric models, especially IRI model (Ezquer et al, 1995(Ezquer et al, , 1999Zhang et al, 2004Zhang et al, , 2007Solomon 2006;Wang et al, 2009, among others). Using ionograms data obtained in the period 1958-1982, Ezquer et al (1996, 2003 have checked the validity of IRI to predict the critical frequencies of the ionospheric regions and the maximum electron density of the F2 region (NmF2) and its height (hmF2), over South American stations.…”