Electrical corona from water-drop surfaces

The results of a recent investigation are used to help clarify the mechanisms of onset and development of electrical discharge from water-drop surfaces exposed to a high field. It is shown that the mechanism determining onset need not be that involved in subsequent development. Thus at about atmospheric pressure, the cause of discharge is surface instability; development produces corona. The different onset fields for positive and negative corona should cause negative charging of highly stressed drops even at atmospheric pressure. The recognition of both positive and negative corona processes from water allows explanation of several puzzling observations, including those of Macky (1931).