Ionization and particle transfer in an expanding current-carrying plasma

A theory is developed for steady-state spherical expansion of a current-carrying plasma that is fully ionized at the transition point to supersonic flow. It is shown that there exists a small region of the initial part of plasma flow where the charge particle density has a maximum and the ions move in a direction opposite to the plasma. The appearance of such a counterstreaming ion current may be of interest when interpreting the plasma–cathode surface interaction in a vacuum arc discharge.