Equilibrium and resistive steady state of an axisymmetric co-axial helicity injection plasma

Steady state (∂B/∂t=∂v/∂t=0) coaxial helicity injection (CHI) has a purely electrostatic E =-∇Φ(ψ,θ) field. The electrostatic potential implies an ExB flow that scales with the externally imposed voltage and is negligibly affected by plasma dissipation. Both the electrostatic potential and the magnetic configuration in the resistive steady state description can be significantly different from those in a Grad-Shafranov open field line equilibrium for CHI discharges. The Bx∇Φ flow in a resistive steady state induces localized perpendicular current for force balance with the plasma inertia. The perpendicular current can drive far stronger parallel current that is localized poloidally on a flux surface. This effect is pronounced for CHI discharges because the desirable CHI hollow current profile has interior high q and there is a magnetic X point in the neighborhood of the absorber, where a large ψ gradient of q and poloidal field strength exists