Earth-Air Electric Currents

Abstract

The paper describes a method for automatically recording the electrical current which passes from the earth into the air during periods of fine weather. A large plate (17 metres2) was placed in the open as near to the ground as was consistent with efficient insulation, this was then connected to an insulated vessel from which water issued through an orifice surrounded by an earth-connected cylinder. The water as it dropped from the insulated vessel carried away, by the well-known collector action, all the charge which the exposed plate received and the latter remained at zero potential. The charged water drops were collected in a vessel connected to a self-registering electrometer which was earth-connected for an instant at the end of every two minutes. The paper describes the sources of error and the method of determining the value of the earth-air current and of the conductivity of the air from the records of the electrometer. The method was used in Simla (India), but owing to the impossibility of obtaining a site on which the normal electrical field of the atmosphere was undisturbed by the surrounding hills and trees, the absolute values obtained were uncertain, but it is very probable that the daily range of the different factors were near approximations to the truth.