International reference ionosphere: Recent developments

An introduction to the history and intentions of the International Reference Ionosphere (IRI) is given and future plans are outlined. The description of the topside electron density profile in the IRI is based on Bent's summary of topside sounder measurements, mainly Alouette. Instead of Bent's tabular form, the IRI has the advantage of an analytical description. Our comparison with AEROS satellite data shows that the IRI model is inaccurate in its description of the latitudinal behavior of the electron density in the topside ionosphere close to the magnetic equator. An improved IRI formula is proposed that closely follows the experimental data. The present IRI is restricted to solar activities reached during the last solar cycle 20. Measurements during the present solar cycle indicate a saturation effect for very high solar activities.