Radiation of the conductive lightning channel

We unify the classical theory of photo-recombination radiation in thermodynamically equilibrium plasma in which the contribution of each final state does not depend on the temperature, and measurements of plasma parameters for the conductive lightning channel. It was shown that this plasma is optically thin one. Maximum plasma temperature of lightning return stroke is nearly of 30 kK. It is restricted by the sharp increase of radiation power with temperature, more that 90% of radiation is found in the vacuum ultraviolet spectral region. We suggest to include the classical radiation theory into the modern computer calculations of lightning models, since then the energy balance of plasma is fulfilled.