Thermal pinch in tokamak plasma

Experiments on different tokamak have shown the existence of so-called thermal pinch, i.e., the tendency toward constriction of the temperature profile. The most impressive of such phenomena was observed recently in the DIII-D tokamak where the inward transport of energy was detected in experiments with off-axis electron cyclotron heating. The heat flow in the direction of increasing temperature seems to be in contradiction with thermodynamics. We discuss this matter from the standpoint of nonequilibrium plasma self-organization. (author)