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.