= Field-line angular velocity of an axisymmetric wind
{title2=$\mathbf u=k\mathbf B/\rho+R\omega(\psi)\mathbf e_\phi$}
In steady axisymmetric <ideal magnetohydrodynamics>, induction makes $\omega$ constant on regular connected <poloidal flux surfaces>. It describes field-line rotation. The material angular <velocity> is $u_\phi/R=\omega+kB_\phi/(\rho R)$ and differs when the toroidal <magnetic field> contributes. If the <poloidal magnetic field> vanishes, the flux-surface integration requires separate treatment.
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