000231276 001__ 231276
000231276 005__ 20190228220014.0
000231276 0247_ $$2doi$$a10.1063/1.4803914
000231276 022__ $$a1070-664X
000231276 037__ $$aARTICLE
000231276 245__ $$aFluctuating zonal flows in the I-mode regime in Alcator C-Mod
000231276 269__ $$a2013
000231276 260__ $$bAmerican Institute of Physics$$c2013
000231276 336__ $$aJournal Articles
000231276 520__ $$aVelocity fields and density fluctuations of edge turbulence are studied in I-mode [F. Ryter et al., Plasma Phys. Controlled Fusion 40, 725 (1998)] plasmas of the Alcator C-Mod [I. H. Hutchinson et al., Phys. Plasmas 1, 1511 (1994)] tokamak, which are characterized by a strong thermal transport barrier in the edge while providing little or no barrier to the transport of both bulk and impurity particles. Although previous work showed no clear geodesic-acoustic modes (GAM) on C-Mod, using a newly implemented, gas-puff-imaging based time-delay-estimate velocity inference algorithm, GAM are now shown to be ubiquitous in all I-mode discharges examined to date, with the time histories of the GAM and the I-mode specific [D. Whyte et al., Nucl. Fusion 50, 105005 (2010)] Weakly Coherent Mode (WCM, f = 100–300 kHz, Df/f approx. 0.5; and k_theta approx. 1.3 cm-1) closely following each other through the entire duration of the regime. Thus, the I-mode presents an example of a plasma state in which zero frequency zonal flows and GAM continuously coexist. Using two-field (density-velocity and radial-poloidal velocity) bispectral methods, the GAM are shown to be coupled to the WCM and to be responsible for its broad frequency structure. The effective nonlinear growth rate of the GAM is estimated, and its comparison to the collisional damping rate seems to suggest a new view on I-mode threshold physics.
000231276 700__ $$aCziegler, I.
000231276 700__ $$aDiamond, P.H.
000231276 700__ $$aFedorczak, N.
000231276 700__ $$aManz, P.
000231276 700__ $$aTynan, G.R.
000231276 700__ $$aXu, M.
000231276 700__ $$aChurchill, R.M.
000231276 700__ $$aHubbard, A.E.
000231276 700__ $$aLipschultz, B.
000231276 700__ $$aSierchio, J.M.
000231276 700__ $$aTerry, J.L.
000231276 700__ $$0240123$$g176719$$aTheiler, C.
000231276 773__ $$j20$$tPhysics of Plasmas$$q055904
000231276 909CO $$ooai:infoscience.tind.io:231276
000231276 909C0 $$0252028$$pSPC
000231276 909CO $$pSB$$particle
000231276 909C0 $$xU12272$$xU12268$$xU10558$$xU10635$$xU12266$$xU10636$$xU10137$$xU12270$$xU10557$$xU12273$$xU10559$$xU12271$$xU12269$$xU12267$$xU10136
000231276 917Z8 $$x176719
000231276 917Z8 $$x173008
000231276 937__ $$aEPFL-ARTICLE-231276
000231276 973__ $$rREVIEWED$$sPUBLISHED$$aOTHER
000231276 980__ $$aARTICLE