Normal and abnormal region-e ionisation

An account is given of the variation of normal and abnormal region-E ionisation through the sunspot cycle. While the solar ultra-violet light responsible for the production of normal region E varies markedly through the cycle, it is found that such radiation may not be expressed as a single-valued function of mean sunspot numbers, the solar radiation being greater for a given sunspot number during years of rising solar activity than during years when the activity is falling. Normal and abnormal region-E ion-productions have not been found to vary similarly during years of varying solar activity.