THE CRITERION FOR PROPAGATION OF THE POSITIVE STREAMER AND ITS APPLICATION

Through analysing the upward leader from a tall structure under storm condition,it is concluded,in this paper,that the intense electric field in a limited,small region provides the necessary condition for the natural lightning discharge to occur.Such a "local intense field" could make it possible that a weak streamer grows and continues to travel in ambient field of only several tens of kilovolts per meter,which otherwise,could propagate only in the ambient field of several hundreds of kilovolts per meter.Based on the positive streamer theory and energy-balance limitation,we have deduced a criterion for detormining whether the positive streamer propagates continuously or not.Using this criterion,we derive the striking distance for tall structures,and the electric environment for artificially triggering lightning by rocket launching with grounding wire.Both results agree with observations.