Changes of Lower Ionosphere Electron Densities with Solar Zenith Angle


  • E. A. Mechtly,

  • L. G. Smith


The University of Illinois and the GCA Corporation launched a series of four Nike Apache rockets from Wallops Island, Virginia, on July 24, 1968, for the study of changes of lower ionosphere electron densities with solar zenith angle on the same day. An improved method of data analysis is outlined. Profiles of electron density for each of the four rockets are presented and compared with two profiles from years of quiet sun, 1964 and 1965. Evidence is found for an initial increase of free electrons followed by a decrease and then an increase in electron number density as the solar zenith angle changes from 94° to 18°. This pattern suggests a sequence of processes; i.e., electron detachment, recombination, and photo-ionization.