Observations and modeling of lightning leaders

The development of atmospheric lightning is initiated by a 'leader' phase during which ionized channels appear in virgin air. The use of rapid cameras. the measure of fields and currents associated with the discharge allow one to compare the propagation of laboratory leaders with those of natural or artificially triggered lightning. The corresponding physical processes can be analyzed with the help of models developed for laboratory leaders provided that the non linear effects due to the intense current circulation leading to lightning leader thermalization are taken into account. A self-coherent simulation of triggered lightning leaders for both polarities is presented is this paper. Furthermore, these models make it possible to define the 'stabilization field' concept, equal to the minimum ambient field allowing the stable progress of a leader from a around structure, expressed as a height and curvature function of this structure. This concept can be validated through triggered lightning tests. Finally the stabilization field analysis is completed by a simplified analytical model based upon all electrostatic approach of propagation equilibrium.