Plasma parameters in the channel of a long leader in air

The time evolution of the electric field in the leader channel and other characteristics of the leader plasma in long air gaps are simulated. Calculations are performed in the one-dimensional time-dependent model with allowance for the time-varying energy deposition in the channel, the channel expansion, and the nonequilibrium ionization kinetics in the leader plasma. The calculations show that, at a gas temperature of 4500-6000 K, associative ionization 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 under the conditions typical of the leader discharge. The calculated electric field agrees well with the data from the experimental modeling of long leaders by a spark discharge in short gaps. (C) 2001 MAX "Nauka/Interperiodica".