Scaling laws of density fluctuations in tokamak plasmas

Fluctuation measurements provide key elements for turbulent transport analysis. In scaling experiments, they bring complementary local information for validating confinement dependence on nondimensional parameters. The scaling of spatial and temporal characteristics of the fluctuations allows a more detailed comparison with transport models. This article will review the fluctuation observations of the scaling experiments in different tokamaks. They concern mainly scaling laws with the normalised gyroradius rho*. This article also presents another aspect of fluctuations dependence, the scaling with the wavenumber, which provides information on the nonlinear turbulence mechanisms.