The Coast-Line Effect on Rapid Geomagnetic Variations

Abstract

Calculations are made for the magnetic field of the induced currents in a hemispherical ocean by a uniform inducing field which is either parallel or normal to the axis of the ocean. The conductivity of the ocean is assumed infinite, an assumption permissible when rapid variations are considered. The results show that a large concentration of induced currents exists near the coast, and that the effect of this concentration of currents is to reverse the direction of the vertical component on land and that of the horizontal component at sea near the coast. This is the effect noted by Parkinson at Watheroo. It is shown that the oceanic shielding is reduced due to currents induced in the Earth's core. However, the enhancement of the field near the coast remains.