A set of transport equations is analysed, including the bifurcation of theradial electric field in toroidal helical systems. Calculations are madesimulating the compact helical systems experiments. Both hard and softtransitions are found in the profile of the radial electric field. Whether theelectric domain interface exists or not is found to depend on the ratio of theelectron temperature to the ion temperature. The structure of the electricdomain interface is also studied. The steep gradient of the radial electricfield is obtained and the width of the electric domain interface is determinedby the anomalous diffusivity of the electric field. The region where theelectron root and ion root co-exist is obtained when changing the density orthe heating power of electrons. The various types of the electrostaticpotential structures are found. The condition for the turbulence suppressionis examined in the parameter regime studied here.
Control of the radial electric field shear by modification of the magnetic field configuration in LHD