Field reversal in the negative glow of a DC glow discharge

We present a simple analytical derivation of the position of the field reversal in the negative glow of a dc glow discharge. In the absence of charged particle losses, this position is shown to depend only on the relaxation length of the energetic electrons entering the glow, the sheath length and the gap length. The model shows that the position of the field reversal, if it exists, can be deep in the negative glow plasma; it is not necessarily at the sheath-negative glow boundary. A large part of the total number of ions created in the negative glow can therefore enter the sheath and return to the cathode. These model results are independent of the electron temperature in the glow.