The temperatures and constituents of the upper atmosphere

Abstract

In a previous paper attention was drawn by one of us to the fact that the upper ionized, F, region of the ionosphere tended to reach a minimum height in the early morning. A study of the results of other workers reveals the world-wide nature of this effect, which is readily observable in both English and American published data. Any method of measurement of the height of the ionized regions of the atmosphere yields the “equivalent height" z' = ∫ z 0 0 dz /μ, where z 0 is the height to which the measuring radio wave penetrates, and μ is the refractive index of the intervening medium at the height z . It follows that a temporal change in z' may be due either to a change in z 0 or to a change in the height distribution of μ ( i. e. , of N the ionization density per cc). We cannot therefore be certain, in general, whether the occurrence of a minimum in z' indicates a true minimum height of the F ionized region, or a readjustment of ionization in and below this region.