Dynamics of streamer propagation in air

Results concerning the dynamics of streamer propagation in air under a unif orm electric held are presented and discussed. Experiments were performed i n a plane-parallel electrode arrangement with positive streamers initiated at a sharp point in the earthed anode. The basic properties of streamers ar e described in terms of the electric field required for a stable propagatio n and the associated propagation velocity. Critical parameters are the ambi ent electric field, the voltage used for streamer initiation and the distan ce of traverse. The present experiments permit the separation between the e ffects of the above parameters upon streamer advancement and propagation ov er the whole path up to the cathode. It is shown that an intrinsic propagat ion field with an associated velocity can be defined, which determine the p ropagation of streamers of a limiting, minimum energy. The propagation velo city is a power function of the electric field and, with the aid of an empi rical equation, values can be expressed accurately in terms of these intrin sic streamer properties.