Electric discharges produced by clouds of charged water droplets in the presence of moving conducting object

•Moving conductors can initiate electric discharges from artificially charged clouds.•Cloud–projectile–ground discharge involves two positive leaders with similar speeds.•Return-stroke-like process is always observed in projectile-initiated discharges.

The possibility of initiation of electric discharges by a crossbow bolt (projectile) moving in the electric field of a cloud of negatively charged water droplets has been demonstrated for the first time. Over one hundred of discharges have been produced. For each event, a high-speed video camera recorded the images of upward positive leaders developing from both the nearby grounded sphere and the projectile, followed by the return-stroke-like process. Corresponding currents were measured and integrated photos of the events were obtained. The results can help to improve our understanding of lightning initiation by airborne vehicles and by a vertical conductor rapidly extended below the thundercloud in order to trigger lightning with the rocket-and-wire technique.