Characteristics of the discharge of a charged dielectric in low-pressure air

A charged dielectric generates a series of discharges in the surrounding air when the pressure is steadily reduced from near atmospheric to fractions of a torr. The dielectrics here employed were Mylar and Teflon. With positive polarity different discharge regimes were observed as the pressure varied: spark and long streamers at relatively high pressure; diffuse cloud-like discharges below 266 Pa (2 torr). With negative polarity it is difficult to induce a discharge, due to the absence of an electron-emitting surface. Similarities between our results and some of the features of mesospheric and stratospheric discharges are discussed.