Experimental Investigation on the Magnetic Double Refraction of Ionised Air

Abstract

THE theory of the propagation of electromagnetic waves in the ionised upper atmosphere of the earth, as influenced by the earth's magnetic field, has been developed by Appleton¹, Hartree², Goldstein³ and others. Investigations on the magnetic splitting and polarisation of radio waves returned from ionospheric layers have confirmed this so-called magneto-ionic theory. Laboratory experiments have also been carried out in this connexion. Benner⁴, for example, has shown that at the approach of the critical value of the magnetic field (He/mc = the angular frequency of the incident waves), the values of the refractive index and the conductivity of a space containing free electrons change abruptly. Similar observations have been made by H. Gutton⁵, and by Jonescue and Mihul⁶. Appleton and Childs have shown⁷ that at this value the absorption of waves is greatly increased.