Plasma parameters in the channel of a long leader in air

The time evolution of the electric field in the leader channel and other ch aracteristics of the leader plasma in long air gaps are simulated. Calculat ions are performed in the one-dimensional time-dependent model with allowan ce for the time-varying energy deposition in the channel, the channel expan sion, and the nonequilibrium ionization kinetics in the leader plasma. The calculations show that, at a gas temperature of 4500-6000 K, associative io nization becomes a dominant ionization mechanism in the leader channel; as a result. the electric field decreases to 100-200 V/cm in 10(-4)-10(-3) s u nder the conditions typical of the leader discharge. The calculated electri c field agrees well with the data from the experimental modeling of long le aders by a spark discharge in short gaps. (C) 2001 MAX "Nauka/Interperiodic a".