The F Region during Magnetic Storms

The results are described of statistical investigations made in the F region during magnetic storms. The characteristics of the daily variation of the deviation from the mean critical frequency and of the height of the maximum electron density, Δf0F2 and ΔhPF2, respectively, are shown over the wide range of latitude from the equator to the auroral zone and for the principal seasons of the year. After a brief survey of theories to interpret the observed results, it is shown that the ionization-drift theory, which is associated with the dynamo theory, is almost satisfactory for the consistent interpretation of the various facts observed.