Evidence of the gaseous nature of positive filamentary streamers in various liquids

Positive filamentary streamers in liquids have been the subject of a large number of experimental investigations, but their physical nature and the mechanisms involved during their propagation have not been fully determined. In models the streamer filament is assumed to be a more or less conducting medium, but its physical nature is not considered in detail. The purpose of this paper is to present the results of experiments carried out in different liquids, including nonvolatile liquids (silicone oil, cyclooctane), and transformer oil.