A thermospheric model of the annual variations of He, N, O, N2, and Ar from the Aeros Nims data

A model of the annual variations of He, N, O, N2, and Ar was derived from the Aeros A and Aeros B neutral and ion mass spectrometer (Nims) data at two local times, 4 and 16 hours, in the altitude range 220–550 km. The Aeros data represent conditions near a solar minimum during the period December 1972 to September 1975. Using the analytical framework of the Ogo 6 model, the number densities of the constituents were expanded into spherical harmonics and the temperature inferred from N2 observations under the assumption of diffusive equilibrium. The average exospheric temperature 〈T∞〉 = 835 K (Kp = 1; 〈F10.7〉 = 80) is in excellent agreement with Thuillier's model value of 840 K (M1 model) but lies about 20 K above the corresponding temperature of the MSIS model. The familiar constituents He, O, N2, and Ar were extended by atomic nitrogen which was deduced from the 30‐amu mass peak. At the poles this constituent shows a density pattern similar to N2 and at the equator like O, but with a much stronger diurnal variation.