Review of claimed enhanced lightning protection of buildings by early streamer emission air terminals

Simple air terminals are earthed conducting objects able to launch a connecting streamer or leader discharge that intercepts a downward lightning leader discharge and diverts to itself the lightning strike. Early streamer emission (ESE) air terminals are claimed to initiate the connecting streamer earlier in time than would a simple air terminal in the same position, and are therefore claimed to be able to attract the lightning discharge from a larger distance than would a simple air terminal. The chief objection raised is that this implies that a streamer or leader discharge from an ESE air terminal is able to continue propagating when the electric field ahead of the advancing tip of the streamer or leader is below the minimum value that would apply to a streamer or leader from a simple air terminal. Once a streamer or leader discharge has propagated into the space remote from the air terminal, its further progress depends upon the supply of energy from the electric field in the space near the tip of the discharge and upon the dielectric properties of the air undergoing breakdown. As neither of these factors can be influenced by the air terminal, it is concluded that it is not possible to gain a significant improvement in lightning interception performance by causing the early emission of a streamer from an air terminal.