The cause of storm after effects in the middle latitude D-region.

A quantitative description is presented of the ionization induced by middle latitude energetic electron precipitation. An evaluation is conducted of the precipitation mechanism which proceeds through a combination of wave turbulent pitch angle diffusion and atmospheric scattering. It is expected that during the recovery phase of a major geomagnetic storm electron precipitation will dominate all other known D-region ionization sources with the possible exception of X radiation during solar maximum conditions.