  Floating potential structures that are correlated over a long distance are
observed with a 2D probe array in the plasma edge of the TJ-II stellarator. We
introduce a method based on the Singular Value Decomposition to extract the
spatio-temporal structure of the global, fluctuating, zonal-flow-like floating
potential from the combined measurements of a 2D probe array and a distant
single probe. The amplitude of these global structures is seen to modulate not
only the high k-poloidal spectral power of the local turbulence, but also
particle transport into the unconfined Scraped-Off Layer, as observed by
H-alpha monitors around the device. These observations provide the first direct
evidence of the global modulation of transport by zonal flow-like structures.
The ability to identify spontaneous and collective rotation events with flux
surface symmetry opens up the possibility to perform unperturbative studies of
the effective viscosity in stellarators and tokamaks.
