The structure of the streamer zone of an impulse discharge of positive polarity in a needle-to-plane air gap is observed with high spatial resolution for two cases: for gaps with and without a thin dielectric plate (barrier) placed along or at a certain distance to the gap axis. The experiments are carried out with two amplitudes and shapes of the applied voltage pulse (impulse length about 800 and 360 ns). The discharge structure is analysed using a CCD camera and dust figure technique. It is shown that the discharge characteristics such as shape and amplitude of the discharge current, the streamer zone length and structure depend on the permittivity of the barrier, its thickness, its surface state and its position relative to the needle electrode. With a closer position the influence of the barrier is more pronounced, but in all cases of the barrier present in the gap, including the case when the barrier touches the needle electrode, a volume part of the discharge is detected in addition to the surface discharge. The structure of the streamer zone of the discharge at different conditions is analysed.

No abstract

No abstract

Application of the artificial clouds of charged water aerosol capable to initiate discharges inside clouds and between cloud and ground could help on the solving of problem of separation of the lightning intracloud and ground discharges, and establishment of connections between the parameters and the spectral characteristics of discharge current impulses and its electromagnetic radiation. Results of analysis of spectral characteristics of discharge from artificial thundercloud and radiation created by them in near field using two kinds of wavelets are presented. Characteristics frequency ranges for different stages of discharge formation and its radiation are analyzed. Comparison between the discharge current parameters and the parameters of its electromagnetic radiation and wavelet characteristic frequencies has been fulfilled. Application of received results to the analysis of electromagnetic radiation signals registered during the different stages of lightning is discussed.

No abstract