Influence of E x B and delB drift terms in 2-D edge/SOL transport simulations

Classical particle drifts across the magnetic field can play an important role in tokamak edge-plasma transport. The relative influence of these terms is studied for self-consistent simulations by including them, together with anomalous diffusion transport, in a 2-D fluid model of edge-plasma transport for the DIII-D tokamak geometry. The drifts cause asymmetries in the plasma parameters between the inner and outer divertor regions which depend on the direction of the magnetic field, B. The basic results can be understood by dividing the drifts into three categories: diamagnetic, E x B, and del B. The dominant effect near the divertor plates is from the E x B drifts, while the weaker del B drifts cause an increase in the magnitude of the radial electric field inside the magnetic separatrix. The diamagnetic terms, defined here as divergence free, do not contribute to transport. (C) 1999 Elsevier Science B.V. All rights reserved.