A self-consistent theory of radial transport of field-aligned current by microturbulence

The radial transport of field-aligned current resulting from collisionless microturbulence is examined self-consistently. The self-consistent treatment of mode coupling is shown to constrain the transport in such a way that the relaxation of current gradients is regulated solely by electrostatic fluctuations that couple to ion dissipation, even in the presence of temperature gradients and temperature anisotropy. As a consequence, the radial flux of parallel current induced by collisionless microinstabilities is insufficient to account for the dynamo in reversed field pinch plasmas.