Physical properties of the atmosphere between ∼80 km and ∼250 km

It is the purpose of this paper to extend the knowledge of the atmosphere to greater heights by suggesting a set of equations which incorporate some of the physical facts which seem to be known, at least qualitatively. A relation between the fractional change of concentration with change in height is proposed, which gives the possibility of determining the change in molecular weight with altitude, provided a temperature and its gradient are known at a datum level. Molecular weight calculations have been carried out for the region between 80 km and 250 km by assuming molecular oxygen dissociates between ∼80 km and ∼120 km, and molecular nitrogen dissociates between ∼130 km and ∼250 km, assumptions which will be discussed below. The set of equations has been used to calculate pressure and density from 80 km to 160 km, that is, up to an altitude where the calculated values can be compared with the experimental values obtained from rocket results [see 1 of “References” at end of paper]. A rather close agreement between the two sets of data has been obtained. A comparison between the particle density of molecular oxygen and the radiation flux from the sun, responsible for the dissociation of oxygen, has been made and also gives acceptable results. Nevertheless, one may regard this approach as satisfactory only in a semi-quantitative way, because of the rather simple form chosen for the fractional change of concentration with height. But in view of the uncertainties involved in determining absorption and recombination coefficients, etc., as functions of height, it is believed that the proposed treatment gives correctly the essential features such as total pressure, mean molecular weight, density, and particle concentrations of the atmosphere at the altitudes considered.