Diurnal and seasonal changes in structure of the midlatitude quiet ionosphere

T ypical examples of N (h) data from a seri es of NBS publications on ionospheric electron densities arc described briefly a s an introduction to data available from a one-year's prog ram b eginning during the International Geophysical Cooperation, 1959. The entire body of data is then illustrated in compact form, and discussed phenomenologically. In a synthesis and intE'l'pretation, it is concluded t h at diurn al, seasonal, and latitudinal temperature variations in the F region may explain many features of the quiet-day behavior of t hat region. A corpuscular component of heating at mid and high latitudes is suggested as accounting for the seasonal anomaly in t he daytime F region; t he anomaly is assigned to the summer season rat her than to winter, on the basis of evidence given. The nighttime electron density variatio ns a rc found to be explain able by the loss rate at the equilibrium height to which the laye r drifts under the influence of diffusion. An appendix discusses the day-to-day va riability of the data.