Relations between the diurnal and annual variations of Earth currents, terrestrial magnetism and atmospheric electricity

An investigation is made as to correlations in the diurnal and annual variations of earth‐currents, with those of terrestrial magnestism and atmospheric potential‐gradient, as based on the observations at the Ebro Observatory, Tortosa, Spain, for the magnetically‐quiet days during the five‐year period, 1914–1918.It is found that the diurnal and annual variations of the horizontal components (X towards north, and Y towards east) of terrestrial magnetism are of such a character, quantitatively and qualitatively, as to indicate that only to a certain extent may they ba the direct electromagnetic effects of the observed corresponding earth currents (W towards west, and N towards north). On the other hand there is a high probability that the observed earth‐currents may be the combined result of a varying magnetic field and a varying electric field as indicated by the rate of variation in terrestrial magnetism and atmospheric electricity, during the day and year. The correlation between the variations of earth‐currents and the rate of variation, or time‐gradients, of the atmospheric potential‐gradient is found to be even higher than that for the time‐gradients of terrestrial magnetism, both as regards the diurnal variation and the annual variation.