AERONOMIC PROCESSES IN THE IONOSPHERE.

The approximate variation of the solar flux over the solar cycle is discussed. It is shown that at twilight the variation of the atmosphere over a solar cycle becomes more important than the variation of the solar flux in determining ionic production. The variation of the solar flux being more important for an overhead sun. Practical solutions for the optical depth of the terrestrial ionosphere are given. The nighttime ionosphere is described in terms of stationary decay schemes. Various explanations are brought forth for the nighttime E-region which appears to be the only section of the nighttime ionosphere which departs from stationary decay. The twilight ionosphere is discussed briefly in terms of the behavior of N2 ions. Departures from photoequilibrium are determined. It is noted that the twilight ionosphere is an ionosphere which involves the maximum departure from photoequilibrium. Considering all possible factors, but neglecting sporadic effects, it is shown that uncertainties in reaction rate coefficients remain the major physical ionospheric problem. Approximate ranges for some the important rates are suggested. The temperature dependence of dissociative recombination, a key problem, is also discussed. Author