Diurnal variation of atomic hydrogen in the thermosphere

Abstract

The diurnal variation of atomic hydrogen concentrations in the thermosphere is calculated from the time-dependent continuity and diffusion equations for a range of exospheric temperatures using Jacchia's formulation for the thermal and density structure of the background atmosphere. The magnitude of this variation at the critical level is similar to that obtained by approximate methods, but the details are very different. The diurnal behavior of atomic hydrogen at the critical level is insensitive to the conditions near the turbopause. As a consequence disturbances at the critical level are largely damped out when they reach the turbopause.