An analysis of the empirical models and the measurement results of the polar atmospheric composition at 120–150 km height

Abstract

δ = (O/N 2) exp/(O/N 2) mod ratios are analysed for the polar thermosphere depending on the season and the heliogeophysical activity where (O/N 2) exp values are measured at high latitudes with radiofrequency mass spectrometers at MP-12 rocket launchings and (O/N 2) mod values are calculated for the corresponding conditions of every experiment from 4 models (DTM, MSIS-77, MSIS-83 and Köhnlein model (KL)). The analysis reveals certain regularities in variations for different models. In summer δ DTM does not depend on the heliogeophysical activity and is within a factor of 2–3 for the polar cap and the daytime cusp at 150 km; during the polar night δ DTM depends on the geomagnetic disturbance and varies with the solar activity cycle. The δ MSIS-77 and δ KL values have little dependence on the heliogeophysical conditions and have approximately the same seasonal variations. During the polar night δ MSIS-83 corresponds to 1 ± 0.25 at high and low solar activity. The increase in δ dispersion for every model considered is noted at low solar activity in the morning and evening sectors of the auroral oval.