The origin of large scale density fluctuations and their role in electron t
ransport has been investigated in the Madison Symmetric Torus reversed-fiel
d pinch [R. N. Dexter , Fusion Tech. 19, 131 (1991)]. At medium frequencies
(10-30 kHz), (n) over tilde is associated with core-resonant magnetic fluc
tuations having poloidal mode number m=1 and toroidal mode numbers n=6-10.
These chord-averaged density fluctuations are shown to be coherent with lar
ge scale radial flow fluctuations, permitting fluctuation-induced particle
flux of the form <(n) over tilde(v) over tilde (r)> to be studied. In the e
dge, although amplitudes are large, (n) over tilde and (v) over tilde (r) a
re out of phase, consistent with advection of the mean density gradient by
perturbed magnetic field lines and no electron transport. During improved c
onfinement discharges, produced by inductive current drive, both fluctuatio
n amplitudes and the total radial electron flux are greatly reduced over th
e entire plasma cross section. (C) 2001 American Institute of Physics.