XV International Conference on Atmospheric Electricity, 15-20 June 2014, Norman, Oklahoma, U.S.A.
We have observed for the first time the intracloud discharge with plasma parameters close to the parameters recorded in the long spark discharges. Plasma structures occurred in the artificial highly charged aerosol clouds of the negative and positive polarities. These plasma structures were recorded with the use of a high-speed IR camera (of wavelength 3.8-4.9 μm) simultaneously with the visible radiation recorded by high-speed visible cameras and photomultiplier tubes (PMTs) with interference filters. The wavelength range of the IR camera gave to us a unique possibility for diagnostics of the structures within the cloud formed by drops with a typical radius of 0.5 μm. The plasma structures found in the positive and negative clouds differ substantially. Elongated discharge channels are often organized into different clusters of the complicated structure. The thermal-ionization instability is discussed as a common mechanism of the plasma channel formation in the observed discharges and the natural cloud and cloud-to-ground discharges.
For the first time a junction of two leaders one of which is formed in an aerosol cloud was recorded in a direct experiment, and it was shown that the parameters of the front of the current and its duration are very similar to those corresponding to the return stroke in resultant long spark discharges. The junction occurred between a downward negative leader from a cloud of negatively charged water aerosol and an upward positive leader from a grounded plane. Additional information about the characteristics of this process was obtained by means of high speed video and infrared cameras.
The possibility of modeling of altitude-triggered lightning (ATL) under laboratory conditions using charge initiation by a crossbow bolt, in the electric field of an artificial cloud of a negatively charged water aerosol, has been demonstrated for the first time. Over one hundred of such events have been registered. For each event, a high-speed camcorder recorded the dynamics of the upward positive leaders with streamer corona, followed by a return stroke and channel plasma decay. Integrated photos of the events have also been obtained. Simultaneously, we measured the current flowing through the bolt in the plasma channel. A similarity of the discharge initiated by the bolt in the electric field of an artificial cloud of charged aerosol to the altitude-triggered lightning in nature is discussed.
Presented is the project of the microwave diagnostics, intended for measuring the absolute value and dynamics of space-averaged conductivity of plasma in the streamer zone and the sheath of a long spark and plasma inside the artificial charged aerosol cloud during a discharge process. The first results of artificial charged aerosol cloud discharges investigation with use of the microwave diagnostics are obtained. By weakening the probing microwave radiation was measured absolute value and dynamics of space-averaged electron density in the cloud during discharges initiated by grounded metal ball.