RELAXATION OF A 2-SPECIES MAGNETOFLUID AND APPLICATION TO FINITE-BETAFLOWING PLASMAS

The relaxation theory of a two-species magnetofluid is presented. This generalizes the familiar magnetohydrodynamic (single-fluid) theory. T he two-fluid invariants are the self-helicities, one for each species. Their ''local'' invariance follows from the helicity transport equati ons, which are derived. The global forms of the self-helicities are ex amined in a weakly dissipative system. They are shown to pass three te sts of ruggedness (''relative'' invariance compared with the magnetofl uid energy): the cascade test; the selective decay test; and the stabi lity to resistive modes test. Once ruggedness is established, relaxed states can be found by minimizing the magnetofluid energy subject to c onstrained self-helicities. The Euler equations are found by a variati onal procedure. Example equilibria are presented that resemble field-r eversed configurations (FRC) and tokamaks. These states are characteri zed by finite pressure and significant sheared flows. Throughout the a nalysis it is shown how this more general theory reduces to the magnet ohydrodynamic (single-fluid) theory for suitable reducing assumptions. (C) 1998 American Institute of Physics. [S1070-664X(98)00407-8]