Electric field recovery after lightning as the response of the conducting atmosphere to a field change

Computations are presented to show that the rearrangement of space charge existing in the fair weather conductivity profile of the atmosphere can explain the observed rapid recovery of electric field after a lightning flash without invoking a core of high conductivity within the cloud or charge at the cloud boundary. An exponential conductivity profile accurately accounts for the first second of observed recoveries at the ground, predicting increasingly rapid recoveries at greater distances. The whole of the rapid recoveries observed above clouds is also explained, but the suggestion that recoveries become even more rapid at higher altitudes remains to be verified by observation. The conductivity near the ground is less than that given by the exponential profile, and if the model is restricted to include only the clear air above the cloud, the complete recovery curve at all distances on the ground is explained, while recoveries above the cloud are unaffected. The slight but significant deviations from the exponential form of distant recoveries observed on the ground are also accurately forecast. The simple Coulomb field of a regenerated charge within the cloud cannot result in more rapid recoveries after distant discharges than after close ones.