On interrelation between inward turbulent flux and lower order rational magnetic surfaces at plasma edge

The interrelation between experimentally measured inward turbulent flux and lower order rational magnetic surfaces is demonstrated by the example of system with externally imposed magnetic surfaces – L-2M stellarator [Plasma Phys. Control. Fusion 50, 045001 (2008)]. In this note we show that average turbulent flux change sign from outward to inward in the vicinity of lower order rational magnetic surface located at plasma edge. There exists an upper threshold in plasma density for inward flux observation.