Runaway breakdown and hydrometeors in lightning initiation
A. V. Gurevich and A. N. Karashtin
Accepted
The particular electric pulse discharges are observed in thunderclouds during the initiation stage of negative cloud-to-ground lightning. The discharges are quite different from conventional streamers or leaders. The detailed analysis reveals that the shape of pulses is determined by runaway breakdown of air in the thundercloud electric field initiated by extensive atmospheric showers (RB-EAS). The high amplitude of pulse electric current is due to the multiple micro discharges at hydro meteors (HM) stimulated and synchronized by the low-energy electrons generated in RB-EAS process. The series of specific pulse discharges leads to charge reset from HM to the free ions and creates a numerous stretched ion clusters, both positive and negative. As a result, a wide region in the thundercloud with a sufficiently high fractal ion conductivity is formed. The charge transport by ions plays a decisive role in the lightning leader preconditioning.