Evidence for a lack of diffusive control of the atmospheric sodium layer

If the final loss of atmospheric sodium occurs in the same height range as its initial entry to the atmosphere, then vertical transport will have little influence on the total abundance of sodium although it could affect its vertical distribution. If, on the other hand, as suggested by a number of recent models, the final sink for sodium is situated well below the layer, and the sodium density depends on a chemical quasi-equilibrium between free sodium and sodium compounds, then the sodium density will be approximately inversely proportional to the eddy diffusion coefficient. An examination of the experimental evidence suggests that eddy diffusion does not play an important role in controlling the total abundance of sodium, thus suggesting that the final loss of sodium must occur in the same height region as its initial input.