Dynamics of the lower thermosphere consistent with satellite observations of 5577 Å airglow: II. Atomic oxygen, local turbulence, and global circulation results

Abstract

Satellite airglow observations in conjunction with a model for the photochemical and dynamical processes in the altitude range 80 to 120 km have been used to obtain the global and temporal variations of atomic oxygen concentration, eddy diffusion, and circulation. The concentration of atomic oxygen shows midlatitude peaks near equinox, and minima about one month after solstice. Average values at midlatitudes are about 1.3 times those at the equator. Small scale turbulence decreases away from the equatorial region in the postequinox period, while near solstice the turbulence is stronger and more uniform with latitude. At equinox, poleward meridional winds of 5–10 m/s are accompanied by upward winds at the equator and downward winds at midlatitudes. There is a slow transition from the dynamics occurring at equinox to those at solstice. At solstice, vertical wind velocities near 110 km of about 10–15 cm/s are upward in the summer and downward in the winter. About one month after solstice, the strength of global dynamics (both turbulence and circulation) reaches a maximum and the global atomic oxygen concentration is lowest. At this time a summer-to-winter flow occurs at high altitudes (> 110 km) accompanied by a return meridional flow below about 105 km.