Theory and simulation of rotational shear stabilization of turbulence

Journal Article · Fri May 01 04:00:00 EDT 1998 · Physics of Plasmas

DOI:https://doi.org/10.1063/1.872847· OSTI ID:627773

Waltz, R E; Dewar, R L; Garbet, X ^[1]

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1. General Atomics, P.O. Box 85608, San Diego, California92186-5608 (United States)

Numerical simulations of ion temperature gradient (ITG) mode transport with gyrofluid flux tube codes first lead to the rule that the turbulence is quenched when the critical E{times}B rotational shear rate {gamma}{sub E{sub {minus}}crit} exceeds the maximum of ballooning mode growth rates {gamma}{sub 0} without E{times}B shear [Waltz, Kerbel, and Milovich, Phys. Plasmas {bold 1}, 2229 (1994)]. The present work revisits the flux tube simulations reformulated in terms of Floquet ballooning modes which convect in the ballooning mode angle. This new formulation avoids linearly unstable {open_quotes}box modes{close_quotes} from discretizing in the ballooning angle and illustrates the true nonlinear nature of the stabilization in toroidal geometry. The linear eigenmodes can be linearly stable at small E{times}B shear rates, yet Floquet mode convective amplification allows turbulence to persist unless the critical shear rate is exceeded. The flux tube simulations and the {gamma}{sub E{sub {minus}}crit}{approx}{gamma}{sub 0} quench rule are valid only at vanishing relative gyroradius. Modifications and limits of validity on the quench rule are suggested from analyzing the finite relative gyroradius {open_quotes}ballooning-Schr{umlt o}dinger equation{close_quotes} [R. L. Dewar, Plasma Phys. Controlled Fusion {bold 39}, 437 (1997)], which treats general {open_quotes}profile shear{close_quotes} (x variation in {gamma}{sub 0}) and {open_quotes}profile curvature{close_quotes} (x{sup 2} profile variation). {copyright} {ital 1998 American Institute of Physics.}

• OSTI ID: 627773
• Report Number(s): CONF-971103--
• Journal Information: Physics of Plasmas, Journal Name: Physics of Plasmas Journal Issue: 5 Vol. 5; ISSN PHPAEN; ISSN 1070-664X
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
BALLOONING INSTABILITY
PLASMA SIMULATION
SHEAR
TURBULENCE