The formation mechanism of a steep structure in the radial electric field is one of the key issues in transport barrier physics. Previous analyses for obtaining the radial electric field structure were carried out with flux surface averaged quantities [1]. On the other hand, the appearance of a poloidal shock structure has been suggested when the poloidal Mach number approaches one [2], which is obtained in improved confinement states. The shock position depends on the poloidal Mach number, and the combination of the radial E × B flow shear and the poloidal shock model in Ref. [2] changes the radial electric filed profile. The existence of the shock structure also suggests generation of a non-negligible radial flow. Therefore, a model coupling the radial and poloidal structure is needed for a quantitative analysis to understand the mechanism of steep structure formation. The radial and poloidal structures can be coupled by taking account of shear viscosity and the radial flow which affects the convecting term. The shear viscosity gives a typical scale length [3] and affects to make structures smooth. We give a self-sustained 2-D structure model, and solve its special case taking account of the shear viscosity only. Interaction between quantities in different flux surfaces through the shear viscosity reveals a 2-D structure in tokamaks and make possible to evaluate whether the radial flow is negligible or not.

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