Note on the electrical waves occurring in nature

Abstract

It has often been pointed out that whenever a lightning discharge occurs between a cloud and the earth, or between two charged clouds, it must give rise to a violent disturbance of the local electrical field, which will spread outwards as an electric wave from the region of the discharge. A lightning discharge may be aperiodic or oscillatory; accordingly a solitary wave or a train of waves, as the case may be, travels in all directions from the centre of discharge till its energy is dissipated by divergence into space or by the absorption of the atmosphere, and thus the disturbance may reach great distances. In wireless telegraphy these vagrant waves are a source of great trouble to the telegraph operator. Being often very intense pulses or trains they frequently set the receiving autenna, whatever its natural period may be, into more violent vibration than do the signals being listened for, and not infrequently they compel the complete suspension of traffic. By those engaged in wireless telegraphy, all these and similar disturbances are called, variously, “atmospherics,” “strays,” “statics,” or “X’s.” When the usual telephonic method of receiving the Morse dots and dashes is employed, the strays are heard in the telephone as sharp clicks, as rattling noises, or as prolonged grinding or fizzing sounds. There is no doubt that some of these noises are due to other causes than vagrant waves. For example, it is well known that wind-driven hail, snow, or rain, produce in an earthed antenna transient currents that can affect the resonant circuits and the telephone of the receiving apparatus, and other very local causes are conceivable. But the travelling waves mentioned above, it has sometimes been surmised, form a considerable proportion of the strays heard on any occasion. It is the purpose of the observations described below to settle whether the proportion of strays due to vagrant waves of distant origin is indeed of importance. If it is, then the general properties of these waves, the limits of distance through which they can travel, and their meteorological significance (if any), all seem worthy of investigation. The particular point we are here enquiring into does not seem to have been investigated before. The sum total of the work published on the whole subject is very small, and no investigations specially directed towards the discrimination of the various causes are known to us.