ELMs and Strike Point Jumps
If an ELM is a peeling of flux surfaces from the plasma, due to a broken separatrix, current density is lost as well as particles and energy. The fast loss of a current-carrying plasma layer modifies the plasma equilibrium, leading to sudden shifts in the strike points at each ELM, towards the plasma centre. An experimental study of this conjectured model of the ELM was made at JET, showing that in all cases studied (type I ELMs) strike point shifts were observed. In two cases studied in detail, the equilibrium changes agree qualitatively with the observed shifts.