(TH/2-6) Plasma and Momentum Transport Processes in the Vicinity of a Magnetic Island in a Tokamak

**Abstract.** In the vicinity of a magnetic island, the toroidal symmetry of
the equilibrium magnetic field strength B is broken in tokamaks due to the
finite width of the island. The magnitude of the broken symmetry is of the
order of the square root of the perturbed magnetic field strength. This
leads to enhanced plasma transport in the vicinity of the island. The ratio
of the symmetry-breaking-induced heat flux to that of the banana regime flux
can be significantly greater than unity in low collisionality regimes. The
magnitude of the island-induced transport fluxes can be comparable to that
of the anomalous transport fluxes. It is also shown that these
symmetry-breaking-induced fluxes are driven by the toroidal pressure
tensor. The toroidal momentum can, thus, be affected. Island-induced fluxes
can change the toroidal rotation. Finally, the radial electric field in the
vicinity of the island can be determined from the momentum balance. We find
the momentum equation is a nonlinear function of the radial electric
field. It can have bifurcated solutions. Thus, in the vicinity of a magnetic
island, plasma confinement can have high(H)-mode like phenomenon.

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*IAEA 2003*