Generation of Diffuse Jets and Runaway Electron Beams in Air, SF6, and Helium at Low Pressures

Abstract

Nanosecond discharges in air, SF₆, and helium at pressures of units–tens of Torr are studied. Spatial inhomogeneities of diffuse jets and autographs of runaway electron (RAE) beams are recorded in all three gases during a discharge in a nonuniform electric field. It is shown that diffuse jets change their shape and their lengths increase and change from pulse to pulse in the discharge gap as the pressure decreases; further, it is confirmed that the RAE beam amplitude increases as the gas pressure decreases. It is assumed that inhomogeneities observed in the diffuse jets and RAE beams can be associated with transient luminous events in the Earth’s atmosphere that have sizes of tens of kilometers and occur at high altitudes at low pressures under high thunderstorm activity.