  In a wide variety of natural and laboratory magnetized plasmas, filaments
appear as a result of interchange instability. These convective structures
substantially enhance transport in the direction perpendicular to the magnetic
field. According to filament models, their propagation may follow different
regimes depending on the parallel closure of charge conservation. This is of
paramount importance in magnetic fusion plasmas, as high collisionality in the
scrape-off layer may trigger a regime transition leading to strongly enhanced
perpendicular particle fluxes. This work reports for the first time on an
experimental verification of this process, linking enhanced transport with a
regime transition as predicted by models. Based on these results, a novel
scaling for global perpendicular particle transport in reactor relevant
tokamaks such as ASDEX-Upgrade and JET is found, leading to important
implications for next generation fusion devices.
