Some of the Chief Problems in Terrestrial Magnetism and Electricity

Abstract

The early completion of the general magnetic survey of the globe, as undertaken by the Department of Terrestrial Magnetism of the Carnegie Institution of Washington and cooperating countries, will afford the necessary data for the investigation of some of the so-called “greater problems of the earth's magnetism.” One of these is the determination of the various systems of magnetic and electric forces which together make up the total terrestrial magnetic field as observed at the earth's surface. It is known from previous analyses that the earth's magnetic field consists of an internal system of forces, which constitutes by far the major portion; secondly, an external system, supposedly to be ascribed to electric currents circulating in the earth's atmosphere; and, thirdly, a system possibly such as that of vertical electric currents which pass from the atmosphere into the earth and vice versa. The definite settlement of the question as to the existence of the third system is regarded by Sir Arthur Schuster as one of the chief outstanding problems in terrestrial magnetism. This problem involves the question whether or not the magnetic forces of the earth can be entirely referred to a potential. If not, then the question arises as to the existence of vertical electric currents, which will be of interest both to students of the earth's magnetism and of the earth's electricity, using the latter term in its most general sense so as to include electric phenomena arising from systems both below and above the earth's surface. The ocean work of the Department of Terrestrial Magnetism has been arranged with the special view of obtaining the requisite data for the solution of this interesting question. But for the war all the necessary data and the results of their discussion would be available now.