On the dynamics of blobs in scrape-off layer plasma: Model validation from two-dimensional simulations and experiments in Tore Supra

An investigation is proposed on the dynamics of blobs in scrape-off layer (SOL) plasmas. Starting from a common reduced model predicting the dynamics of isolated blobs, we emphasize the necessity of verifying the meaningfulness of the notion of generic or average blob. A definition and methodology is proposed and tested on turbulent data built from two-dimensional (2D) flux-driven simulations. Average blobs are shown to possess physical properties in relatively good agreement with predictions made using the isolated blob model. An application to experimental data from Tore Supra is then demonstrated. A striking agreement is found between average blob velocities measured in experiments and isolated blob model predictions. It suggests that the turbulent transport in the SOL of limited plasmas is correctly described by 2D interchange models. A discussion is finally proposed that blob models have to focus on intermittency in order to find a field of application.