The Franklin lightning conductor: conditions necessary for the initiation of a connecting leader

The attachment of a lightning flash to a Franklin conductor takes place thr ough a connecting leader that rises from the Franklin rod towards the down coming stepped leader of the lightning flash. The successful launching of a connecting leader requires the inception of a streamer discharge from the rod and its transformation into a leader (i.e. streamer to leader transitio n). Here, the occurrence of these physical processes at the tip of the Fran klin rod is investigated. The results shows that for Franklin conductors of radii less than about 0.35 m artificial initiation of streamers at the con ductor tip would not result in any increase in the attractive distance. For rod of radii larger than 0.35 m it may be possible to launch a connecting leader by artificially triggering of streamer discharges at the conductor t ip but the gain in attractive distance would not be larger than about 30%. (C) 2001 Elsevier Science B.V. All rights reserved.