Transport suppression by diamagnetic phase shift as a possible mechanism of the low to high mode transition
- Fusion Research Center, The University of Texas at Austin, Austin, Texas 78712 (United States)
- Department of Physics, University of California at San Diego, La Jolla, California 92093-0319 (United States)
In the presence of a pressure gradient, the phase velocity of drift wave or ion temperature gradient (ITG) mode turbulence is different from the average poloidal {bold E}{times}{bold B} rotation velocity of the guiding centers. This results in an {tilde E}{times}{bold B} turbulent particle diffusion being suppressed by the phase shift due to the diamagnetic rotation velocity {ital u}{sub {theta}}=({ital c}/{ital enB}){ital dP}/{ital dr}. This shift cannot be eliminated by a change of frame and affects the plasma transport. For {ital u}{sub {theta}} well above the turbulent {tilde E}{times}{bold B} velocity, the radial diffusivity is suppressed as {ital D}{proportional_to}{ital u}{sup {minus}3}{sub {theta}}. This results in a nonmonotonous particle flux {Gamma}({del}{ital n}){congruent}{minus}{ital D}{sub 0}{del}{ital n}[1+{alpha}({del}{ital n}){sup 2}]{sup {minus}3/2} such that the transport can develop a bifurcation at a realistic density gradient.
- DOE Contract Number:
- FG05-88ER53266; FG03-94ER54241
- OSTI ID:
- 63681
- Journal Information:
- Physics of Plasmas, Journal Name: Physics of Plasmas Journal Issue: 6 Vol. 2; ISSN PHPAEN; ISSN 1070-664X
- Country of Publication:
- United States
- Language:
- English
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