Field Criterion for Sustained Streamer Propagation

Experiments have shown that streamers are astonishingly capable of penetrating low-field regions before finally coming to a stop. This lead to a proposed theory of low-field requirements for continued propagation of the ionizing potential space wave constituting the streamer. The long range of impulse streamers in atmospheric air from a positive point was investigated in order to establish their spatial properties and a criterion that allows the prediction of such ranges. This was accomplished by axial and lateral measurements of the ranges of streamers for various gap spacings. A parallel study based on charge simulation and using a digital computer delivered the field intensity at the various points of the gap. The correlation of the results of both studies showed that streamers tend to stop whenever the applied field drops below 500 to 600 V/cm regardless of gap spacing or streamer location. Thus, streamers are not capable of propagating under an external zero field and require this minimum field for sustained advance.