Magnetic fluctuations and energy transport in RFX

In thermonuclear fusion plasmas, transport losses are usually believed to be caused by turbulent fluctuations. Particularly in the outer region of tokamaks, stellarators and reversed field pinches, electrostatic turbulence accounts for particle transport. In tokamaks, electrostatic fluctuations can also be responsible for the radial energy flux; in reversed field pinches, energy transport cannot be ascribed to electrostatic turbulence only. In the plasma edge of the reversed field experiment device, identified as the region between the toroidal field reversal and the first wall, an extensive study of magnetic fluctuations and of the related radial energy flux has been performed. It is found that magnetic fluctuations carry most of the radial flux of energy. However, close to the wall the magnetic fluctuation-driven energy flux decreases abruptly, so that another mechanism must be invoked. There are indications that the energy flux channel in this region is the macroscopic magnetic deformation due to the phase locking of magnetic modes.