Blocking streamer development by plane gaseous layers of various densities

Streamer interaction with gaseous layers of various densities is numerically simulated in ambient air on the basis of a two-dimensional fluid model. It is shown that rarefied layers are greater obstacles to streamer propagation in comparison with dense layers. When intersecting a low-density layer, the streamer tends to initiate a radial ionization wave, which screens and weakens the electric field both on the axis in the layer and behind it. As a result, it is difficult to form a secondary streamer behind the low-density gas layer. A streamer interacting with a high-density layer also can initiate a radial ionization wave, which develops in undisturbed air along the outer surface of the layer. The streamer can overcome a high-density layer at not-too-high values of the layer thickness. The effects of the streamer polarity, layer thickness and density on the streamer interaction with the layer are studied. It is shown that the discharge gap with a thin low-density layer behaves like a diode in which streamer discharges of negative polarity can pass through the gap, while discharges of positive polarity are blocked.