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Drift hole structure and dynamics with turbulence driven flows

Published Web Location Commons 'BY-NC-ND' version 4.0 license

The role of turbulence driven flows in describing drift hole structure and dynamics is discussed. Turbulence driven flows enter the plasma medium response and alter drift hole structures by changing the screening length of the drift hole potential. Specifically, turbulence driven flows shift the drift hole potential radially, and absorb drift hole energy via the hole-flow resonance. It is shown that the absorption shifts the phase of a momentum flux, and so enables the irreversible coupling of drift holes to turbulence driven flows. We show that drift holes and turbulence driven flows are dynamically coupled, and self-regulate each other, so that a stationary state can be achieved with non-zero turbulence driven flows. As an application, a bound on the fluctuation amplitude in the coupled system is derived. The bound is obtained by requiring that the resultant zonal flow velocity should be smaller than the critical flow velocity for the drift hole potential to be self-bound (i.e., the velocity that the screening length be positive). The result predicts m a x 2 ∼ (ν d / ω c i) (k / k y), where zonal flow damping appears as a control parameter. The implications of this result for the problem of edge-core coupling (i.e., explaining turbulence and transport in No Man's Land) are discussed. © 2012 American Institute of Physics.

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