Electron trapping by electric field reversal and Fermi mechanism

We investigate the existence of electric field reversal in the negative glow of a dc discharge, its location, the width of the well trapping the electrons, the slow electrons scattering time, and the trapping time. Based on a stress-energy tensor analysis we show the inherent instability of the well. We suggest that the Fermi mechanism is a possible process for pumping out electrons from the trough, interrelated with electrostatic plasma instabilities. A power-law distribution function for trapped electrons is also obtained. Analytical expressions are derived which can be used to calculate these characteristics from geometrical dimensions and the operational parameters of the discharge.