Correlations of Elm Frequency with Pedestal Plasma Properties

JET data for the correlations between pedestal plasma temperature and density with the frequency of different type ELMs are analyzed in the framework of a classical Focker-Planck approach. In first approximation we derive a functional dependence in steady state of ELMs assuming equality between the outward flux of plasma from the core and the loss of plasma from the pedestal into the SOL. In this assumption one expects equality between ELM frequency and Coulomb collisionality in the pedestal plasma. Our analysis of JET and TCV data shows that the derived formula for density dependence on temperature is obeyed in wide range of ELM size (including ELM III) but with varying coefficient that corresponds to the configurations of the engineering parameters. The values of this constant differ from that in the FockerPlanck solution for diffusion transport indicating the impact of non-diffusion transport.