Solitary radial electric field structure in tokamak plasmas

The solitary structure solution of the radial electric field E-r in the tokamak plasmas is obtained. It is shown to be stable under an external power supply, like a biased electrode at the edge. The radial gradient is governed by the ion viscosity and the nonlinearlity of the perpendicular conductivity. The radial structure of E-r and reduction of turbulent transport, which belong to key issues of the high confinement mode (H-Mode) [F. Wagner et al., Phys. Rev. Lett. 49, 1408 (1982)], are self-consistently determined. A bifurcation from a radially-uniform one to a solitary one occurs at a certain applied voltage, and a hysteresis is associated. (C) 1998 American Institute of Physics. [S1070-664X(98)01312-3].