(TH/P3-1) MHD Flow Layer Formation in Vicinities of Rational Flux Surfaces of Tokamak Plasmas

Abstract.  The crucial role of sheared flows in formation of external and internal transport barriers (ITBs) in advanced tokamak discharges has been demonstrated in recent decades. Two sources driving such flows have been identified in the studies. The first is the mean sheared flows created by external sources and/or gradient of plasma pressure. The second is the zonal flows formed in nonlinear interaction of small scale turbulent fluctuations through wave coupling or inverse cascade. A third kind flow, MHD flows, is proposed and studied in this work. The driving mechanism for the MHD flows is the magnetic energy released in reconnection process of tearing mode nonlinear development. The flows have the same helical structure as the magnetic field at the resonant surfaces in the toroidal and poloidal directions. They are confined in the vicinities of the resonant surfaces and have strong shear at the boundaries of the reconnection layer. The radial structure and the amplitudes of the flows are estimated to be compatible with the requirements for suppression of transport producing turbulences. The possible correlation of the flows with ITB formation is discussed.

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