An Effect of Catastrophic Ionospheric Disturbances on Low-Frequency Radio Waves

Abstract

RECENTLY there has been much interest in those catastrophic ionospheric disturbances which are supposed to produce ‘radio fade-outs’ on highfrequency radio waves and short-lived disturbances in the terrestrial magnetic records. In a recent report, Dellinger¹ has given an account of the results of these disturbances, based on more than a year's observations by workers in different parts of the world, and he states that “ordinarily the intensities of the waves received from radio stations on frequencies below about 1,500 kc./s. are not perceptibly affected during a fade-out". He mentions, however, that Bureau² has found an increase in the number of atmospherics on frequencies between 27 and 40 kc./s. during many of the disturbances ; this is the only evidence so far published that the propagation of low-frequency waves is affected at these times.