Relaxation of a Two-Specie Magnetofluid

Abstract

The relaxation theory of an ideal magnetofluid is developed for a multispecie magnetofluid. Its invariants are the self-helicities, one for each specie. Their ``local'' invariance in the ideal case follows from the helicity transport equation. The global forms of the self-helicities are investigated for a two-fluid (ion and electron), and their ruggedness in a weakly dissipative system is defended by cascade and selective decay arguments. In general the two-fluid theory predicts relaxed states with finite pressure and sheared flows. The familiar single-fluid relaxation theory, which admits only force-free states, is a reduced case of the present more general theory.