Advanced specification of electron density and temperature in the IRI ionosphere–plasmasphere model

A plasmasphere extension has been incorporated in the International Reference Ionosphere, IRI*, using the Russian standard model of the ionosphere, SMI, at altitudes from 1000 km to the plasmapause (⩽36,000 km). The IRI model has been improved using global space–time statistics of the half-width of the topside ionosphere estimated from ISIS1, ISIS2, and IK19 satellite observations. Chebishev orthogonal polynomial approximations of the topside half-width of the electron-density profile, normalized to the F2-layer peak height for the ranges of geomagnetic latitude, local time, and solar activity, are incorporated in the IRI electron-density profile. Comparison of the Chebishev model of the topside half-width and its standard deviation with IRI-Bent and ISIS/IK19 data demonstrates an improvement of the IRI-Bent model using the new anchor point in the topside ionosphere. Extension of IRI ionospheric electron temperature towards the plasmasphere is made with a revised model for the electron temperature in the upper ionosphere and plasmasphere. The previous model equation is modified to produce height variations in accord with recent theory and observations. Field-aligned profiles then depend on three parameters, which are determined as a function of latitude by fitting the modified equation to satellite data at heights of 400–10,000 km. This leads to a new global model giving Te as a function of height, latitude, local time and season, with first-order corrections for changes with solar flux and magnetic activity. Estimates of the ion temperature Ti are also obtained. Results represent a mean of current experimental data, and give smooth, physically realistic variations under all conditions.