Rd. Durst et al., OBSERVATION OF A LOCALIZED TRANSITION FROM EDGE TO CORE DENSITY TURBULENCE IN THE TFTR TOKAMAK, Physical review letters, 71(19), 1993, pp. 3135-3138
A localized transition zone is observed between turbulent, long-wavele
ngth density fluctuations (k(perpendicular-to) < 2 cm-1) in the core a
nd edge of beam-heated discharges in TFTR. The core turbulence is unim
odal while the edge has two counterpropagating modes, both of which ar
e spectrally distinct from the core fluctuations. The fluctuation ampl
itude in the core scales with the global energy confinement time while
in the edge it does not. These observations suggest that distinct mod
es are responsible for turbulence in the two regions and that only the
core mode is directly related to global confinement.