where μ μ 0 is the magnetic permeability, p ( ψ ψ ) is the pressure, F ( ψ ψ ) = r B θ θ and the magnetic field and current are, respectively, given by B = 1 r ∇ ∇ ψ ψ × × e ^ ^ θ θ + F r e ^ ^ θ θ , μ μ 0 J = 1 r d F d ψ ψ ∇ ∇ ψ ψ × × e ^ ^ θ θ − − [ ∂ ∂ ∂ ∂ r ( 1 r ∂ ∂ ψ ψ ∂ ∂ r ) + 1 r ∂ ∂ 2 ψ ψ ∂ ∂ z 2 ] e ^ ^ θ θ .