Point discharges

From Glossary of Meteorology
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point discharge

A silent, nonluminous, gaseous electrical discharge from a pointed conductor maintained at a potential that differs from that of the surrounding gas.

In the atmosphere, trees and other grounded objects with points and protuberances may, in disturbed weather, be sources of point discharge current. Close to a pointed and grounded conductor that extends above surrounding objects, the local electric field strength may be many times greater than that existing at the same level far from the elevated conductor. When this local field reaches such a value that a free electron, finding itself acted upon by this field, can be accelerated (in one mean free path) to a sufficiently high velocity to ionize neutral air molecules, point discharge will begin. Different structures will yield point discharge under quite different gross field conditions, for geometry is critically important. Point discharge is recognized as a major process of charge transfer between electrified clouds and the earth, and is a leading item in the charge balance of the global electrical circuit.
Compare corona discharge, spark discharge.