Modeling of dynamic response of SOL-divertor plasmas to an ELM crash

A dynamic five-point model is developed to study responses of scrape-off-layer (SOL) and divertor plasmas to a crash due to edge-localized modes (ELMs). The five-point model is beneficial to wide-ranging studies of SOL-divertor physics and to coupling with the core transport code in the integrated modeling. The five-point model can reproduce static and dynamic features obtained by usual fluid codes. The dynamic behavior obtained by the five-point model agrees fairly well with that by the particle code PARASOL. The influence of the ELM crash on the thermoelectric instability and the resultant asymmetry is investigated. The ELM crash transiently induces the thermoelectric instability and large SOL currents for asymmetric divertor plasmas before the ELM. The resultant currents drive convective heat flows and enhance the asymmetry on the fast time scale of electrons. The ELM crash is found to reverse the asymmetry before and after the ELM. Even for symmetric plasmas before the ELM, the asymmetry is induced on the slow time scale of ions by an ELM crash, because the transient formation of dense and cold divertor plasmas causes the thermoelectric instability.