Information on the D‐ and E‐Region Electron Density Profiles

The paper surveys the available information on the D‐ and E‐region electron density profile. The behavior of the E‐layer peak in time and space is fairly well mapped from ionosonde measurements. Our knowledge of the ionization distribution below the maximum of the E layer comes from a limited number of rocket flights through the lower ionosphere and from extended time series of observations by ground‐based radio methods from a few stations. From such measurements a very sketchy and imperfect picture emerges of the electron density profile in the quiet and disturbed lower ionosphere and its geographical, diurnal, seasonal, and sunspot cycle variation.