Position dependence of the unstable vertical movement of JET plasmas triggered by ELMs

In this paper we report the results of a set of dedicated experiments carried out at JET, aimed at studying the spatial dependence of the excitation of the unstable mode following an edge localized mode (ELM). A dependence of the excitation of the unstable mode on the pre-ELM vertical position can indeed be found, although a neutral point is not present in the explored range. The CREATE-L linearized plasma response model is used to reliably estimate the growth rate and discuss a correct global characterization of ELMs from the point of view of simplified modelling for control. The results indicate that a drop of pressure energy alone is not sufficient but that an increase of magnetic energy should be included.