IMPROVING IRI-90 LOW-LATITUDE ELECTRON-DENSITY SPECIFICATION

At low latitudes under moderate to high solar conditions, a number of comparisons between the international reference ionosphere (IRI-90) mo del of F region electron density profiles and observed profiles measur ed by the Jicamarca incoherent scatter radar indicate that during the daytime the observed profile shape can be much broader in altitude tha n that specified by IRI-90, while at night, just after sunset, observe d F-2 peak altitudes are significantly higher than what is specified b y IRI-90. Theoretically derived ionospheric parameters such as F-2 pea k density (NmF2), F-2 peak altitude (h(m)F(2)), and profile shape, whi ch are contained in the parameterixed ionospheric model. (PIM), have b een shown in some cases to be in better agreement with Jicamarca obser vations. This paper describes a new low-latitude option for IRI-90 tha t uses five ionospheric parameters derived from PIM: the bottomside pr ofile half thickness, NmF2, h(m)F(2), and two parameters of a topside Chapman profile. The generation of electron density profiles using the se five parameters is presented, as well as a description of how these parameters can be implemented into the IRI-90 model.