On the nature of transport in fusion plasmas

A view of the mechanisms underlying particle and energy transport in fusion plasmas devices (tokamak and stellarators) is given. The heat and energy transport in fusion plasmas is generally due to turbulent processes. Several driving ( plasma gradients) and damping ( electric field) mechanisms of turbulence have been investigated. The development of methods to modify and control plasma turbulence by electric field effects has opened a new era on fusion confinement research. Recently, a newapproach based on multi-field probability density function statistical analysis has been proposed to describe transport in non-equilibrium systems and to unravel the overall picture connecting transport, gradients and flows in fusion plasmas.