Wireless Communication and Terrestrial Magnetism

Abstract

THE letters which have recently appeared in NATURE on the relationships of wireless reception and terrestrial magnetism suggest that a few remarks from the point of view of a magnetician may not be superfluous. First, on an historical point, it should be remembered that estimates of the altitude of a stratum of high electrical conductivity were made long before the times of wireless communication. Cavendish (Scientific Papers, vol. 2, p. 233) in 1790 obtained on strictly scientific grounds an estimate of from 84 to 114 km. for the altitude of an auroral arc. Prof. Störmer's methods of high precision have supplied numerous results for the lower level of aurora, which have long been well known. The levels he has found show variations with similar limits to those recently obtained by Appleton and Barnett (Roy. Soc. Proc., A, vol. 113, p. 450). Auroral observations, of course, are not possible by day, and we may hope to learn much from wireless which it might be difficult or impossible to derive from auroral observations.