Scrape-off layer turbulence theory and simulations

Significant investigations in the area of scrape-off layer (SOL) turbulence theory and simulations are reviewed. The paper begins with description and derivation of the various models investigating specific linear modes as well as a discussion of the regions of validity. Special attention is given to various low-frequency electromagnetic drift-types modes in an x-point divertor geometry, which are generally believed to be relevant under normal operating conditions for current and future large fusion devices. The anomalous transport from simulations and from mixing length estimates are discussed and compared with results infered from experiments. Studies of mechanisms for the L-H transition due to turbulent transport in the SOL, and its impact on the II-mode power threshold, are also surveyed.