The induction of electric currents in a non-uniform ionosphere

Abstract

Calculations are made of the distribution and the magnetic field of the currents induced in a non-uniformly conducting ionospheric shell by an external magnetic field, which is either periodic or subject to sudden changes. Assuming that the initial phase of magnetic storms is due to field changes outside the ionosphere, it is shown that its mean integrated conductivity is probably not much greater than 10 -7 e.m.u. It is found that electromagnetic shielding by the ionosphere has an important effect on the distribution of field changes observed on the earth, and may lead to an apparent diurnal variation of frequency of occurrence of sudden commencements at a given station. Simple explanations are suggested for some known features of micropulsations, and for some well-known phenomena of magnetic disturbance, including Sangster’s rotating disturbance vector.