Dependence of positive corona streamer propagation on air pressure and water vapor content

Abstract

Experiments are described in which the ambient electric field required for sustained positive corona streamer propagation is determined as a function of dry air pressure and water vapor partial pressure. This critical field varies approximately as the 1.5 power of the dry air pressure and shows a strong linear dependence on the water vapor partial pressure. These results differ substantially from what would be expected on the basis of Paschen’s Law, but are consistent with a propagation mechanism in which the ionizing streamer tip and a portion of the plasma trail left behind it are treated as an electrically isolated propagating conductor. Energy budget arguments indicate that the critical field is inversely proportional to the length of the trail that is effectively conducting and is dependent, therefore, on the lifetime of low‐energy electrons against attachment.