The International Reference Ionosphere is the standard ionospheric model developed and improved by a joint working group of the International Union of Radio Science and the Committee on Space Research. Based on all reliable and accessible ground and space data, IRI describes monthly averages of the electron density, electron temperature, ion temperature, ion composition, and ion drift at ionospheric altitudes. The newest version of IRI is described in a report, NSSDC/WDCA-R&S 90-22, published by the National Space Science Data Center in November 1990. The book contains sections on history and new developments, formulas and buildup, graphs, and references.
The main difference between IRI-90 and its predecessor IRI-86 are new models for the E-F region electron density and for the ion composition. It was decided to offer these new model choices in addition to the older versions, thus making the transition from old to new version more transparent to the user community.