Transient Response and Transport
It is often assumed that a temporal and spatial scale separation holds between global transport and microscopic fluctuations. This leads to the picture that the change of global profile propagates in space with the diffusion time scale. Scale separation is not always satisfied in plasma turbulence, and the transient responses of inhomogeneous plasma could be different from those described by the diffusion process. See the reviews of [2.30, 2.31, 25.1] for the phenomena of transient responses. Theoretical modelling has been developed recently, and some efforts are illustrated in this chapter.