Model of blue jet formation and propagation in the nonuniform atmosphere

About two decades ago, researchers discovered upward propagating flashes of light originating above thunderstorms. Due to their distinctive, principally blue color, they were named "blue jets" (BJ). The broadly accepted production mechanism of a BJ is through a lightning leader which rises through the nonuniform atmosphere. Specifically, the formation of the initial lightning leader is thought to be governed by the contraction of the current of a streamer flash into a small radius channel. This paper presents results of simulations of the current contraction in the air as a function of both the pressure and convective heat removal time. We have shown that transitions to the contracted state occur in a hysteresis mode that allows both contracted and diffusive states to coexist. We have obtained the critical current for this phase transition and studied the formation and propagation of BJs in the atmosphere through a combination of quantitative models and existing observations of BJs that combine optical images with the data of the electric current carried by the jets.