Numerical analysis of initiation of gigantic jets connecting thunderclouds to the ionosphere

The initiation of giant electrical discharges called as “gigantic jets” connecting thunderclouds to the ionosphere is investigated by numerical simulation method in this paper. Using similarity relations, the triggering conditions of streamer formation in laboratory situations are extended to form a criterion of initiation of gigantic jets. The energy source causing a gigantic jet is considered due to the quasi-electrostatic field generated by thunderclouds. The quasi-electrostatic field is assumed to be axisymmetrical. We calculate the electric fields for different thundercloud charges. The electron dynamics from ionization threshold to streamer initiation are simulated by the Monte Carlo technique. It is found that gigantic jets are initiated at a height of ∼18–24 km. This is in agreement with the observations. The distributions of electron positions and electron energies at different initiation heights are presented. The method presented in this paper could be also applied to the analysis of the initiation of other discharges such as blue jets and red sprites.