The variation of the electric field after lightning and the conductivity within thunderclouds

It has been found that the rate of growth of field following a close lightning discharge is explicable in terms of the regeneration of the dipole by a constant current and a charge loss governed by the fair weather conductivity at the height of the charge. The recovery may be influenced by local point discharge after large field‐changes, but the presence of a core of high conductivity within the cloud need not be invoked. The recovery curves from close flashes are found to be rather irregular and no really useful information concerning the currents generating the dipole of the thunderstorm can be derived from them. As the distance of the storm increases then the recoveries become much more rapid and of reproducible shape. It is suggested that after the discharge the re‐arrangement of the space charge existing because of the conductivity gradient in the atmosphere is responsible for the change of the field observed. Some numerical work gives fair agreement with the observed functional dependence of the initial rate of recovery on the size of the field change. These distant recoveries are the response of the conducting atmosphere to the field change, and can give no useful information about the thunderstorm itself.