Based on the experiments we consider, we predict that the s/1 variations of Pseed will be found to be similar to those of PEF•, and largely to explain them. Finally, we find reasons, based on the similarity of the DRSF variations to s/1 patterns of the average scintillation index, for not using, as is commonly done, such scintillation patterns as substitutes for PEF• or Pinst patterns.

Abstract. Some examples from the Atmosphere Explorer E data showing plasma bubble development from wavy ion density structures in the bottomside F layer are described. The wavy structures mostly had east-west wavelengths of 150-800 kin; in one example it was about 3000 kin. The ionization troughs in the wavy structures later broke up into either a multiple-bubble patch or a single bubble, depending upon whether, in the precursor wavy structure, shorter wavelengths were superimposed on the larger-scale wavelengths. In the multiple-bubble patches, intrabubble spacings varied from 55 km to 140 kin. In a fully developed equatorial spread F case, east-west wavelengths from 690 km down to about 0.5 km were present simultaneously. The spacings between bubble patches or between bubbles in a patch appear to be determined by the wavelengths present in the precursor wave structure. In some cases, deeper bubbles developed on the western edge of a bubble patch, suggesting an east-west asymmetry. Simultaneous horizontal neutral wind measurements showed wavelike perturbations that were closely associated with perturbations in the plasma horizontal drift velocity. We argue that the wave structures observed here that served as the initial seed ion density perturbations were caused by gravity waves, strengthening the view that gravity waves seed equatorial spread F irregularities.

Measured values of the atomic‐to‐molecular oxygen concentrations ratio near 120 km are used to determine the strength of turbulent mixing in the atmosphere. Model atmospheres, including some minor constituents, are then derived using an equation that includes the effects of transport by both turbulent mixing and molecular diffusion. It is shown that a convenient and useful definition of the height of the turbopause, which may be at different altitudes for different constituents, is the height at which the vertical component of the eddy mixing coefficient is equal to the molecular diffusion coefficient of the species in question.

Abstract

Horizontal temperature variations contribute to horizontal transport of constituents in an exosphere. If gas concentrations are not uniform, their gradients will also give rise to horizontal transport through the exosphere. The sum of these two transport effects plus the transport due to rotation of the planetary body involved, must balance the integrated sources and sinks of gas in the exosphere, mainly by flow up or down through the base of the exosphere. The relative magnitudes of these effects are evaluated for helium in the earth's exosphere and for neon and heavier constituents in the lunar atmosphere. In the absence of significant sources and sinks the temperature and concentration effects tend to set up distributions such that nT5/2 = constant on the base of the exosphere, but rotation of the planetary body tends to establish distributions such that nT = constant.