Fluid model equations for the tokamak plasma edge

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Abstract
Increasing evidence that the edge plasma plays a crucial role in global tokamak confinement motivates this study of two‐dimensional (2‐D) (θ,r) computational models of fluid transport in the edge plasma region. Fluid plasma equations, boundary conditions, and a coupled neutral–plasma model are developed assuming toroidal symmetry. A plasma potential equation is presented for consistent drift flow solution in the nonambipolar case. Simplified plasma equations are implemented in a 2‐D computational model. Results show large poloidal flux dominated by drift flow near the separatrix and parallel flow near the tokamak divertor target. Simultaneously large poloidal gradients in plasma potential and electric fields are seen. These may play a role in driving observed turbulent fluctuations in the edge plasma.