Self-consistent mean-field forces in turbulent plasmas: Current and momentum relaxation

The properties of turbulent plasmas are described using the two-fluid equations. Global constraints for the fluctuation-induced mean-field forces that act on the ion and electron fluids are derived. These constraints imply functional forms for the parallel mean-field forces in the Ohm's law and the momentum balance equation. These forms suggest that the fluctuations attempt to relax the plasma to a state where both the current and the bulk plasma momentum are aligned along the mean magnetic field with proportionality constants that are global constants. Observations of flow profile evolution during discrete dynamo activity in reversed field pinch experiments are interpreted. (C) 1998 American Institute of Physics. [S1070-664X(98)02606-8]