The heating and the rate of prolongation of the channel of a very long-spark

The process of the heating of heavy particles in the discharge channel of a long spark is analysed in order to derive the relation of the rates of this process in the case of the positive and of the negative space charge in the surroundings of the channel. A special attention is paid to the combined acting of the one-step and two-step mechanism of ionisation of the plasma. There are discussed the causes of the much higher rate of propagation of the negative discharge channel. The theoretical considerations are compared with the results of original experiments with positive and negative discharges of the length up to 60 m. The solution is of a key importance for the analysis of the breakdown process such as very long sparks or the lightning