The physical theory of the Earth's magnetic and electric phenomena.—No. III: the external electric currents and the Earth's magnetization

Abstract

26. The hypothesis of ionic currents employed in the study at the magnetic disturbances thus far treated was based on the existence of a primary electric field. Quoting from No. I, § 11:Since magnetic observations made at various points on the Earth's surface have revealed the existence of a definite system of atmospheric electric currents, it follows at once that if the atmosphere is made more conducting at any point, an extra current will be started and set in motion by the pre‐existent electromotive force or its equivalent. The direction followed by the new current depends upon its origin, upon the direction of the electromotive force at that point, and upon the deflecting effect of the Earth's magnetic field and of the Earth's rotation on the electric carriers. In other words, while we shall look chiefly to extra‐terrestrial agencies for ionizing the air and thus splitting it up into carriers of positive and of negative charges, we look to the atmospheric electric field and to the Earth's rotation for furnishing the energy necessary to drive the ions over the Earth and by their motion produce the effects observed during a magnetic storm.