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AbstractAbstract
[en] Current drive due to helicity injection and the dynamo effect are examined in an inhomogeneous, bounded, visco-resistive plasma. Averaged over a magnetic surface, there is in general no dynamo effect independent of resistivity - contrary to the results found previously for an unbounded plasma. The dynamo field is calculated explicitly for an incompressible fluid in the plane-slab model. In accord with the authors' general conclusion, outside the Alfven resonant layer it is proportional to the resistivity. Within the resonant layer there is a contribution which is enhanced, relative to its value outside the layer, by a factor (ωa2/(η+v)), where ω is the wave frequency, a the plasma radius, η the magnetic diffusivity, and v the kinematic viscosity. However, this contribution vanishes when integrated across the layer. The remaining averaged field in the layer is enhanced by a factor (ωa2/(η+v))+2/3 and is proportional to the shear in the magnetic field and the cube root of the gradient of the Alfven speed. Although the current drive is enhanced in the layer, its efficiency is diminished, relative to outside, where it can be comparable to Ohmic. These results are interpreted in terms of helicity balance, and reconciled with the infinite medium calculations, by noting that the transverse flux of helicity is always proportional to η in the simple fluid model
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Anon; 207 p; 1991; p. 2D31; STI Optronics, Inc; Bellevue, WA (United States); International Sherwood fusion theory conference; Seattle, WA (United States); 22-24 Apr 1991
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Book
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Conference
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