Radio Transmission and Solar Activity

I PROPOSE to review very briefly the progress made in certain branches of radio research since the last General Assembly of the International Scientific Radio Union in 1934. In selecting such topics for consideration I have been constantly struck, as many others doubtless have been, by the way in which the range of the interests of the radio worker has been gradually expanding, so that now it overlaps almost every field of physical knowledge. In that everyday tool we employ, the amplifying valve, we find problems of thermionics, electrostatics and electrodynamics. The study of aerials and their radiative properties involves problems entirely analogous to those of physical optics. The investigation of the travel of radio waves excites our interest in fundamental atomic processes by way of which the electron population in the ionosphere increases and decreases. The profound control maintained by the sun on the ionosphere and, especially, the response of upper atmospheric conditions to events on the sun's surface, identifies our interests closely with those of the solar physicist, while, by way of the troposphere, which is the seat of atmospheric disturbances, we find much of common concern with the meteorologist.