A theory of the permanent magnetic field of the Sun and Earth

Abstract

In this paper (published in full in Phys. Rev., v. 34, 335–343, 1929) the motions of electrons executing short free‐paths under the influence of thermal agitation in an inhomogeneous magnetic field or in crossed electric and magnetic fields is shown to give rise to electric current‐systems. Gravitational separation of charge produces a symmetrical radial electric field inside the Earth and Sun. This radially symmetrical electric field and a small initial symmetrical inhomogeneous magnetic field give rise to current‐systems which are in such a direction as to increase the original magnetic field and regeneration takes place. The field is limited by some mechanism which is not understood. The permanent fields arise from the thermal energy of the body and would be maintained even if the bodies ceased their rotation. In order to account quantitatively for the observed current‐system it is necessary that the electron mean free‐path inside the Earth approximate 10−7 cm. The theory emphasizes the necessity for a better understanding of electrical conduction in solids; in particular a more satisfactory theory of the Hall effect is desirable.