Variational principles for stationary one- and two-fluid equilibria of axisymmetric laboratory and astrophysical plasmas

It is shown that the core equations of both the magnetohydrodynamics and the two-fluid description of stationary axisymmetric equilibrium flows may be derived from variational principles in terms of the core variables of the respective descriptions. The latter replace the primitive variables because of the stream function constraints associated with axisymmetry. This yields a concise representation of stationary flows in tokamaks, accretion disks, and jets, and permits accurate numerical implementation. Since hyperbolic flows occur in both descriptions, the limitation of the variational principles to elliptic flow regimes presents an intricate problem.