V. A comparison of photographic and electrical studies of the discharge process

Abstract

The photographic method of studying the lightning discharge by means of the Boys camera has the unique advantage of giving direct information concerning events in the discharge in two dimensions of space and one of time and could be extended if necessary to include the third space dimension. The luminous events which it records are, however, secondary processes, and the primary movements of electrical charge which cause them can only be inferred by an application of ideas gained from the laboratory study of the passage of electricity through gases. The direct study of these primary electrical processes involves the observation of the electric field during the discharge by means of a cathoderay oscillograph. Studies of near lightning by this method have recently been reported by Appleton and Chapman (1937). The method gives information concerning the total electric moment of the cloud charges and requires to be compared with the photographic data before its results can be interpreted in terms of the charges themselves and their movements.