Contributions to the Mechanisms of the Lightning Stroke*

The writer’s earlier paper on the mechanism of the cloud-to-ground lightning stroke was based on classical observational data. The report on the last 10 years’ observations of strokes from Monte San Salvatore by Berger and Vogelsanger using improved instrumentation calls for a reassessment of the theory and makes possible a tentative extension t o the intracloud stroke mechanisms. The salient new findings from Monte San Salvatore are summarized. The theory of the writer is then considered in terms of the observations. The theory in general is confirmed by these observations and certain more hypothetical conjectures are confirmed by the greater detail available in the new observations. No serious contradictions appear requiring alteration of the theory. Probably the most significant new observations deal with the nature of the positive leader strokes which had not previously been observed in detail. These, together with the very important 1964 observations of Brook and Kitagawa on intracloud strokes, furnish the basis for a tentative analysis of the mechanisms active.