Geomagnetic storms and associated ionospheric effects

Typical examples of ionospheric disturbances associated with geomagnetic storms in various seasons are examined at dip-conjugate low and middle latitude locations along the same longitude. Initial changes were observed in the electron density similar to magnetic field differences followed by changes in F2 ionization controlled by the heating in the upper atmosphere and in the neutral wind pattern. The abnormal increase in F2 electron density during winter at midlatitudes results from the change in the meridional wind pattern and transport from the summer to the winter hemisphere. It is concluded that the post-storm low energy electrons precipitate into the lower ionosphere from the magnetospheric slot and produce a delayed increase in the D-region ionization at midlatitudes.