Amplification and nonlinear modification of runaway breakdown

The astonishing natural phenomenon of narrow bipolar pulses (NBP) is an isolated discharges in thunderstorms at tropopause heights (10-20 km) that generates enormously powerful radio emission but lasts only a few microseconds. The theory of this phenomenon based on runaway breakdown is elaborated. At such high heights extensive atmospheric shower (EAS) become well developed only if the energetic cosmic ray particle momentum is directed close to the horizon. For these conditions the runaway breakdown-extensive atmospheric shower (RB-EAS) discharge amplified strongly what lead to the effective diminishing of thundercloud electric field and results in nonlinear saturation of the discharge current. A reasonable agreement of the theory with NBP observations is demonstrated.