A. Earth Currents


Earth currents constitute a worldwide system of eight loops of electric current rather evenly distributed on both sides of the equator, plus a series of smaller loops near the poles. Although it has been contended that this system is induced entirely by the daily changes in atmospheric electricity (and this may be true for short-term variations), it is likely that the origins of the system are more complex. The core of the earth, which consists of molten iron and nickel, is capable of conducting electricity and can be likened to the armature of a huge electric generator. Thermal convection currents in the core are believed to move the molten metal in loop patterns relative to the magnetic field of the earth, producing the system of earth currents that mirror the pattern of convection currents within the core.


B. The Surface Charge of the Earth


The surface of the earth has a negative charge of electricity. Although the conductivity of air near the earth is small, air is not a perfect insulator, and the negative charge would drain off quickly if it were not being continuously replenished in some way.

In all places in which measurements have been made in fair weather, a flow of positive electricity has been observed to move downward from the atmosphere to the earth. The negative charge of the earth is the cause, attracting positive ions from the atmosphere to the earth. Although it has been suggested that this downward current may be balanced by upward positive currents in the polar regions, the preferred hypothesis today is that the negative charge is transferred to the earth during storms and that the downward flow of positive current during fair weather is balanced by a return flow of positive current from areas of the earth experiencing stormy weather. It has been proved that a negative charge is transferred to earth from thunderclouds, and the rate at which storms develop electric energy is sufficient to replenish the surface charge. In addition, the frequency of storms appears to be greatest during the time of day when the negative charge of the earth increases most rapidly.