A Theory of the Cause of Atmospheric Electricity

Abstract

THE idea that the sun sends out a large amount of Becquerel rays has found considerable support in the scientific world, and has been used to explain a number of difficulties connected with cosmical physics, for example, the source of the sun's energy and comets' tails. There is still another old standing difficulty which it appears to be able to solve, viz. the permanent maintenance of the electrical field in the lower regions of the earth's atmosphere. If we take for granted that the sun continually emits Becquerel rays consisting of positive and negative electrons, one would expect the following to be the consequence. Some of the electrons which reach the earth's atmosphere will be absorbed—probably mainly by the water vapour and dust in the lower atmosphere—but according to Rutherford's experiments more positive than negative; thus we may expect a greater number of negative electrons to reach the surface, a corresponding number of positive electrons being held back by the air. We at once see a cause for the positive charge of the air and the corresponding negative charge on the surface. If there were no “dissipation” the result would be a continual charging up of the atmosphere or an ever increasing potential gradient above the earth's surface; but there is dissipation, and it counterbalances the tendency of the electrical field to increase. If we had a constant dissipation the result would be a maximum potential gradient in the daytime and a minimum in the night, for we must assume that more electrons reach the atmosphere in the day than in the night. But we know from Elster and Geitel's measurements that the dissipation reaches a maximum at midday; this will tend to reduce the maximum of potential gradient which would otherwise be reached about that time. This consideration agrees entirely with the fact, for Exner has described the daily variation of the potential gradient as “a simple daily period, distorted by a midday depression.” With the fairly constant daily period of the entrance of electrons into the atmosphere, the main determining factor of the potential gradient will be the dissipation; thus we find a maximum potential gradient in the winter with a corresponding minimum dissipation. The relation between potential gradient and dissipation has been thoroughly investigated by Elster and Geitel, and they have found experimentally that that which tends to reduce the dissipation tends to increase the potential gradient, which is just what one would expect from the theory. This theory appears to me to be able to account for a great many more of the problems of atmospheric electricity, but the above will show the general idea.