A three-circulation theorem for relativistic plasmas

It is shown that the sum of three circulations (hydrodynamic, magnetic, and thermal) is constant in time for each component of a perfect relativistic plasma. A constraint for the initial configuration (''Weber/Ertel case,'' the lines of canonical vorticity lie on surfaces of constant entropy) leads to zero potential vorticity also for later times; this is generally realized in inhomogeneous flow equilibria for which the explicit time-dependence of Clebsch potentials is given. Equilibrium states of warm relativistic plasmas with vanishing thermal circulation are discussed. (C) 1996 American Institute of Physics.