Diurnal variation of temperature and particle density between ∼100 km and ∼500 km

Abstract

Rocket and satellite observations, made in the U.S.A. and in the U.S.S.R. of atmospheric densities and oxygen ratios n( O) n( O 2) have been used to determine the diurnal variations of pressure, temperature and composition in the region between 100 and 500 km. The six main constituents of the Earth's upper atmosphere have been included : molecular nitrogen and oxygen, atomic oxygen, argon, helium and hydrogen. It has been found that for late 1960: (1) The night-time mass densities are higher than the daytime densities between 100 and about 200 km; the opposite is the case above 200 km. (2) The night-time temperatures are always lower than the daytime temperatures in the region between 100 and 500km. In the exosphere T (night) ≈ 1000° K; T(day) ≈ 1350° K. (3) Between about 110 and 200 km the molecular weight during the night is higher than during the day. Above 200 km the opposite occurs. (4) Between 100 and 160 km the number densities of molecular nitrogen and molecular oxygen are higher during the night than during the day. Above this level the situation is reversed. (5) With regard to the behaviour of hydrogen and helium, it has been found that the number density of the lighter constituent, hydrogen, is higher than that of helium during the night at levels above 250 km. During the day the opposite is true, i.e. the number density of helium during the day is higher than during the night and it is greater than that of hydrogen over the entire region between 100 and 500 km. The results of this investigation have been obtained without assuming a temperature-, scale height-, or molecular weight-gradient, as has been done in previous investigations. It is also the first attempt to make calculations which include major and minor constituents together, based on observed composition data. As a result of this it is shown how the numerical values of composition, and, thus, the role of major and minor constituents, vary with altitude and from day to night.