Core-edge coupling and the effect of the edge on overall plasma performance

Several attempts to model the entire plasma cross section have been reporte d in the last few years. Two possibilities are to either couple a core code to a scrape-off layer (SOL) code at a specified interface or to extend the computational region of an SOL-code all the way to the plasma centre. The most advanced global code is the code COCONUT which is based on the former principle and comprises the Monte-Carlo code NIMBUS, the 2D scrape-off laye r code EDGE2D, the core transport code JETTO and the core impurity transpor t code SANCO. A main feature of COCONUT is its modular structure which ensu res a high degree of flexibility and the capability to cover a large range of time-scales. The influence of the SOL on the core is illustrated with a range of global simulations carried out with COCONUT. The simulations show that the primary effect of the SOL is the control of the particle sources a nd sinks with a secondary effect on plasma dilution, radiation and perhaps pedestal temperatures.