Current filaments in a long spark in air

Recent studies of natural lightning show that the high-energy radiations are generated during thunderstorms. Besides hard x-ray and gamma radiation 1 , neutron generation is also observed 2 . In a laboratory long spark discharge with the parameters similar to lightning the neutron generation is observed also 3 . The model or mechanism to explain the generation of hard x-rays and neutron bursts during atmospheric discharge in air is under discussion.