Increased Nonlinear Coupling between Turbulence and Low-Frequency Fluctuations at the <span class="aps-inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>L</mi><mi>−</mi><mi>H</mi></math></span> Transition

R. A. Moyer; G. R. Tynan; C. Holland; M. J. Burin

doi:10.1103/PhysRevLett.87.135001

Increased Nonlinear Coupling between Turbulence and Low-Frequency Fluctuations at the $L - H$ Transition

R. A. Moyer, G. R. Tynan, C. Holland, and M. J. Burin

Phys. Rev. Lett. 87, 135001 – Published 4 September 2001

Abstract

The nonlinear coupling between small scale high-frequency turbulence and larger scale lower-frequency fluctuations increases transiently in transitions to improved confinement in the DIII-D tokamak. This increase starts before the rapid turbulence suppression and $E \times B$ shear-flow development in the region that becomes the $H$ -mode transport barrier/shear flow region. After the transition, the coupling returns to $L$ -mode levels. These results are consistent with expectations for spontaneous transitions to improved confinement triggered by a turbulence-driven sheared flow.

Received 13 December 2000

DOI:https://doi.org/10.1103/PhysRevLett.87.135001

Authors & Affiliations

R. A. Moyer¹, G. R. Tynan¹, C. Holland^1,2, and M. J. Burin¹

¹Mechanical and Aerospace Engineering Department, University of California, San Diego, 9500 Gilman Drive, La Jolla, California 92093
²Department of Physics, University of California, San Diego, 9500 Gilman Drive, La Jolla, California 92093