Azimuthally symmetric magnetohydrodynamic and two-fluid equilibria with arbitrary flows

Magnetohydrodynamic (MHD) and two-fluid quasi-neutral equilibria with azimu thal symmetry, gravity and arbitrary ratios of (non-relativistic) flow spee d to acoustic and Alfven speeds are investigated. In the two-fluid case, th e mass ratio of the two species is arbitrary, and the analysis is therefore applicable to electron-positron plasmas. The methods of derivation can be extended in an obvious manner to several charged species. Generalized Grad- Shafranov equations, describing the equilibrium magnetic field, are derived . Flux-function equations and Bernoulli relations for each species, togethe r with Poisson's equation for the gravitational potential, complete the set of equations required to determine the equilibrium. These are straightforw ard to solve numerically. The two-fluid system, unlike the MHD system, is s hown to be free of singularities. It is demonstrated analytically that ther e exists a class of incompressible MHD equilibria with magnetic field-align ed now. A special subclass first identified by S. Chandrasekhar, in which t he flow speed is everywhere equal to the local Alfven speed, is compatible with virtually any azimuthally symmetric magnetic configuration. Potential applications of this analysis include extragalactic and stellar jets, accre tion discs, and plasma structures associated with active tate-type stars.