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Fundamental problems of lightning physics are reviewed, and recent advances in the instrumental (primarily satellite) detection of atmospheric discharge phenomena are discussed. The formation of plasma spots with the parameters necessary for the initiation and development of a lightning discharge in a thundercloud is regarded as a nonequilibrium phase transition induced by electrostatic noise. The noise is caused by the collective dynamics of charged hydrometeors, i.e., ice particles and water drops suspended in a convective flow. The interaction of plasma formations and their polarization in a large-scale intracloud electric field ensure the efficient generation of streamers, whose description in terms of random graphs and percolation theory forms the basis for the phenomenological representation of discharge as a fractal dissipative structure. This approach enables solving a number of key problems surrounding thunderstorm electricity, including the lightning initiation mechanism in essentially subthreshold electric fields, the properties and morphology of various types of lightning discharges, and a self-consistent description of the broadband electromagnetic radiation they emit. Prospects for the further development of the model are discussed and the role of forthcoming satellite experiments in the observation of intense electromagnetic radiation from thunderstorm clouds is examined.

Fundamental problems of lightning physics are reviewed, and recent advances in the instrumental (primarily satellite) detection of atmospheric discharge phenomena are discussed. The formation of plasma spots with the parameters necessary for the initiation and development of a lightning discharge in a thundercloud is regarded as a nonequilibrium phase transition induced by electrostatic noise. The noise is caused by the collective dynamics of charged hydrometeors, i.e., ice particles and water drops suspended in a convective flow. The interaction of plasma formations and their polarization in a large-scale intracloud electric field ensure the efficient generation of streamers, whose description in terms of random graphs and percolation theory forms the basis for the phenomenological representation of discharge as a fractal dissipative structure. This approach enables solving a number of key problems surrounding thunderstorm electricity, including the lightning initiation mechanism in essentially subthreshold electric fields, the properties and morphology of various types of lightning discharges, and a self-consistent description of the broadband electromagnetic radiation they emit. Prospects for the further development of the model are discussed and the role of forthcoming satellite experiments in the observation of intense electromagnetic radiation from thunderstorm clouds is examined.

An advanced 3‐D numerical model of lightning development is presented. The key features of the model include the probabilistic branching, bidirectional propagation, nonzero internal electric field, simultaneous growth of multiple branches, physical timing, channel decay, and, for the first time, probabilistic propagation field threshold. The new model can be used for computing electrical parameters of individual branches, including conductivity, current, and longitudinal electric field, each as a function of time, in different parts of the discharge tree. For illustrative purposes, the model was applied to studying the occurrence of lightning flashes of different type depending on the cloud charge structure, with emphasis on the lower positive charge region (LPCR). We demonstrated with the new model that the presence of relatively large (excessive) LPCR can prevent the occurrence of negative CG flashes by “blocking” the progression of descending negative leader from reaching ground. The blocking effect of excessive LPCR was found to occur when the vertical component of electric field near the cloud bottom was negative (downward directed). Further, we showed that significant reduction or absence of LPCR can eliminate the possibility of negative CG flashes and lead to normal‐polarity IC flashes instead. The model predicts the polarity‐asymmetry, which suggests that the amount of collected charge depends not only on the number of branches but also on the dynamics of their conductivity (lifetime) and the local cloud charge density. Three‐dimensional lightning development model taking into account the dynamics of channel heating and coolingProbabilistic field threshold for propagation and simultaneous growth of multiple branches are includedThe model predicts electrical parameters of individual branches

We study the fractal dynamics of the intracloud space charge during the preliminary stage of a lightning discharge, when the so-called drainage system of charge collection from the entire cloud volume is formed. The drainage system is a basis for the initiation of the leader channel of the lightning. This system is formed due to the appearance of electric microdischarges related to the nonlinear stage of the development of an instability of beam-plasma type. The latter is modeled using a two-dimensional lattice of finite-state automata. The results of numerical simulations show that the developed drainage system belongs to the percolation-cluster family. We point out the parameter region relevant to the proposed model, in which the thundercloud exhibits the behavior corresponding to the regime of self-organized criticality. A method for calculating the radio emission from the intracloud microdischarges is proposed, which allows one to compare directly our theoretical model and the experimental data.

A numerical model with physical timing and grid spacing of 3 m is applied to studying the progression (including stepping and branching) of negative lightning stepped leader. The asymmetry between positive and negative streamers is taken into account via using polarity‐dependent initiation and propagation field thresholds. The stepped nature of negative leader is confirmed to be caused by this asymmetry. The step formation process of the negative leader is modeled to begin with the appearance of space stems inside and in the immediate vicinity of its streamer zone (corona streamer burst completing the preceding step). Some of those space stems evolve into space leaders, which can connect to the primary leader channel, thereby facilitating its extension. Model‐predicted morphology and dynamics of negative leaders are in good agreement with the recent recordings of lightning stepped and dart‐stepped leaders obtained using high‐speed video cameras, and their electrical parameters are in line with the current knowledge on negative lightning leaders. Numerical model capable of reproducing the dynamics of negative‐leader stepping and branching processes has been developedModel predictions on leader speed, step length, interstep interval, and charge transfer are in reasonably good agreement with observationsAmong other features current pulses generated at the end of step‐formation process carry positive charge over hundreds of meters upward along the negative‐leader channel

Fundamental problems of lightning physics are reviewed, and recent advances in the instrumental (primarily satellite) detection of atmospheric discharge phenomena are discussed. The formation of plasma spots with the parameters necessary for the initiation and development of a lightning discharge in a thundercloud is regarded as a nonequilibrium phase transition induced by electrostatic noise. The noise is caused by the collective dynamics of charged hydrometeors, i.e., ice particles and water drops suspended in a convective flow. The interaction of plasma formations and their polarization in a large-scale intracloud electric field ensure the efficient generation of streamers, whose description in terms of random graphs and percolation theory forms the basis for the phenomenological representation of discharge as a fractal dissipative structure. This approach enables solving a number of key problems surrounding thunderstorm electricity, including the lightning initiation mechanism in essentially subthreshold electric fields, the properties and morphology of various types of lightning discharges, and a self-consistent description of the broadband electromagnetic radiation they emit. Prospects for the further development of the model are discussed and the role of forthcoming satellite experiments in the observation of intense electromagnetic radiation from thunderstorm clouds is examined.