Simultaneous observations of the Na 5893‐Å nightglow and the distribution of sodium atoms in the mesosphere

Simultaneous laser radar observations of the vertical distribution of sodium in the mesosphere and the intensity of the sodium nightglow show that variations in the glow are well correlated with perturbations in the sodium density. These perturbations have a wavelike structure, with a vertical wavelength of about 10 km, and show downward phase propagation. On most occasions the airglow is best correlated with the density at 88 km, which is about 4 km below the average height of maximum sodium concentration. It is shown that, on the average, a layer 10 km wide centered on 89 km best explains the observed variations. By using current models for atomic oxygen and ozone it is shown that such a distribution is in good agreement with the Chapman mechanism for the sodium nightglow with respect to its height and width but that the calculated emission is about 50 times too small.