The nature of atmospherics. VI

Abstract

In Paper V of this series (Watson Watt, Herd and Lutkin 1937) the results of the early photographic recording of the wave form of atmospherics have been described. It was shown that these rapid changes of the atmospheric potential gradient produced by thunderstorm discharges at quite long distances consist of two distinct oscillatory trains, one having a predominant frequency of the order of 10 kc./sec. and the other about 0.5 kc./sec. The photographic resolution attainable at the time made it impossible to analyse in detail the higher frequency oscillations, and the present paper describes the results of recording on a much more open time scale. This involved the development of a drum camera which could be operated at speeds up to 20 r.p.s. giving film speeds up to 20 m./sec. as compared with 2 m./sec. which was the upper limit attainable by the earlier methods. Two series of observations are discussed. One was made during the autumn of 1934, and consisted of records of atmospherics originating at considerable distances from the receivers. This series, which served to test the methods for improved resolution of the wave form, confirmed the nature of the high-frequency portion of that wave form and emphasized the need for similar records of the atmospherics from storms occurring near to one of the receivers. Such records were obtained in the second series made during the summer of 1936.