Unipolar arc model

A three-dimensional description of an axisymmetric unipolar arc discharge is given. Both sheath and plasma ball effects are taken into account. The analysis is based on the simultaneous solution of Ohm´s law, Maxwell equations, and the boundary conditions for the electric potential at the Plasma-sheath interface. These boundary conditions are dictated by the sheath effects. The potential distribution, current distribution, and magnetic fields in the plasma have been determined for a given electron density profile. These calculations show that the unipolar arc arises as a natural consequence of the pressure force