Influence of Solar Protons on High‐Latitude Ionospheric Disturbance

High‐latitude ionospheric absorption is shown to exhibit a magnetic, rather than local, time dependence. The spatial and temporal variations of absorption are compared to the same variations of impact zones for solar protons in the energy range 50 MeV to 1.0 GeV, and the agreement is shown to be good. Similar agreement is found when various other ionospheric disturbance parameters are considered. The conclusion is tentatively reached that a more or less continuous flux of solar protons is entering the earth's atmosphere, which if valid, would have important consequences in the study of the energy balance of the ionosphere as well as that of the sun itself.