Kohichi Nakamura

Artificially triggered lightning experiments to an EHV transmission line

In a triggered-lightning experiment carried out on a mountain in Japan, thirteen strikes were obtained for the winter seasons of 1986 and 1987. The lightning occurred on the conductor and the tower of a 275 kV test transmission line, on the ground, etc. The authors outline the triggering method and the experimental results obtained from electrical and optical observations. Comparatively intense lightning with a current greater than 50 kA or a charge greater than 200 C was obtained. >

The electric field changes and UHF radiations caused by the triggered lightning in Japan

The electric field changes, the magnetic field changes, and UHF radiation were observed during the rocket-triggered lightning experiment in winter storms. A remarkable discrepancy is noticed between electromagnetic field changes of flashes triggered with a rocket and an isolated wire that struck a power tower and flashes with a rocket and a grounded wire. Flashes to tower have a distinguishable first pulse of a large amplitude, which, we speculate, occurs at the moment of attachment of a downward leader to the tower. The UHF radiation measurements indicate that the triggered lightning process starts with a pulse series resembling a negative stepped leader. The electric field change records of rockettriggered lightning in winter storms do not show the presence of rapid field variations typical for return strokes in natural cloud-to-ground flashes.