Similarities in geomagnetic control on D and F region ionization and possible coupling mechanism

The maximum ionization in the F region is known to exhibit a geomagnetic anomaly with peak ionization around +-30 deg dip and a depression at the dip equator. The so called 'Appleton Anomaly' is not present at sunrise but develops later in the day, persisting for several hours thereafter. The existing literature on the ionospheric absorption of short radio waves is reviewed in the context of F region phenomena. It is shown that close similarity exists in the diurnal behavior and latitudes distribution of ionization at the mesosphere and thermosphere levels, though the intervening E region ionization behaves in a different manner. It is suggested that changes in F region ionization are reflected in the formation of N(2D) concentrations at thermosphere levels which affects the NO concentration around 160 km. This subsequently affects the NO concentration in the mesosphere producing ionization changes similar to those observed near the F region peak ionization. One of the consequences of this is a geomagnetic control of NO creation at low latitudes