An empirical model for the global distributions of density, temperature and effective collision frequency of electrons in the ionosphere

Abstract

An improved ionospheric global empirical reference model (named RIM-85) is established for the distributions of density (N e), temperature (T e) and effective collision frequency ( ν e) of electrons between 65 and 600 km. For altitudes above 200 km, at low and middle latitudes, the N e distribution is based on IRI-82, with some necessary corrections. In comparison with IRI-82 and other models the model RIM-85 has a number of important advantages: (i) it describes in detail the height distributions of N e and T e below 200 km; (ii) it gives for the first time an adequate description of the high latitude ionosphere, its variations with geomagnetic activity reflecting the occurrence and dynamics of the main large-scale structures of the spatial N e distributions; (iii) it describes rather correctly the shape of the N e height profiles at low and high latitudes, in the outer ionosphere and also at high solar activity; (iv) it gives a spatial maximum height distribution of the F-region in the southern hemisphere which is close to the real one and (v) it describes rather correctly the diurnal and seasonal variations of T e. The model RIM-85 is established as a computer program, the general structure of which is similar to the corresponding programs for the IRI-79 and IRI-82 models; it includes some subroutines taken from this model software. Therefore the newly developed model can easily be included into a new version of IRI as a subprogram for N e, T es and ν e calculations.