Electromagnetic Wave Fields near the Earth's Surface

It is shown that in the case of frequencies where the ground wave is of importance any indirect waves can be investigated by keeping within the "sky-wave furrow" of the directional pattern of a loop receptor. Observations indicate multiple downcoming waves in the daytime, with marked changes occurring toward sunset. Conditions during the day are as a rule steady and sometimes resume their steadiness after the sunset fluctuation period. During steady conditions observations were made of the field in the neighborhood of various systems involving boundaries between media of different conductivities, such as horizontal and vertical conductors near the earth's surface and the gorges which characterize the terrain in and about Ithaca. The results are interpreted on the basis of a steady field upon which is superimposed a perturbation field due to a conductor or anticonductor of conductivity ±Δσ. Several ways in which the wave plurality may be accounted for are discussed.