Ionospheric ion composition from satellite measurements made during 1970–1980: Altitude profiles

Abstract

Ion mass spectrometers were carried by a number of satellites in the 1970s. The ion composition measurements from two of these missions, the Orbiting Geophysical Observatory-6 and the Atmosphere Explorer-C, have been collected into an ion composition data base to evaluate several widely used empirical and theoretical models for the species H +, He +, N +, O +, NO +, N 2 +, and O 2 +. The data base covers all latitudes and local times, and the altitude range from 150 km to 1200 km, but here we present altitude plots of the ion densities at noon and at dip latitudes of 20–40° N. The satellite data are compared with an early ion density profile by Johnson, with the Kochnlein and IRI-90 empirical models, and with the Utah State University theoretical ionosphere model. These comparisons serve to verify some aspects of the models, but they also reveal some outstanding differences. The solar activity dependence of H +, He +, N +, and O + is demonstrated, although this has not been possible for the molecular ions because low altitude measurements have not been made near solar maximum.