Compact toroidal plasma equilibrium and implications on stability

The present discussion is limited primarily to the close relationship between the plasma-current-density distribution (mostly poloidal J/sub p/) and the need for an external axial current I0 to prevent unreal singular behavior in the plasma or plasma-vacuum interface. We consider the configuration which is related to spheromaks; the toroidal plasma (p greater than or equal to 0) is nominally in the double-cross-hatched region, and the single-cross-hatched region represents a toroidal vacuum (or force-free pressureless plasma p = 0) region between the spherical separatrix (plus the major axis) and the plasma