Lightning and the long spark

The attractive power of an earthed pointed conductor, rising a short distance out of an earthed plane, for a descending leader stroke to a lightning flash or to a high-voltage impulse discharge has been well established; the laboratory discharge is strongly attracted to such a pointed conductor when the high-voltage electrode is of negative polarity, but not so strongly for a positive-polarity electrode for the same gap spacing. Previous work was done with a fast-front impulse wave. The same results have now been obtained using impulses having wavefronts of 12 and of 160 ?s duration, wavefronts more closely resembling lightning-current wavefronts.