Physics of edge plasmas in enhanced confinement modes

In this article, the physics of various enhanced confinement modes are reviewed. After the discovery of the H-mode, many enhanced confinement modes have been observed. Various kinds of enhanced confinement modes are surveyed first. Typical features of enhanced confinement are the edge pedestal, the density peaking in the core, the modification of the current profile, and the internal transport barrier. Physical processes, which allow these improvements, are explained in terms of the radial electric field structure and magnetic field structure. The influence of the edge and SoL plasma on the core improvement is also explained. An emphasis is made on the role of neutrals in the dynamics of enhanced confinement, illuminating the importance of PSI studies in realizing better enhanced confinement. Perspectives for the steady state plasma are also discussed.