Radial convection of plasma structures in a turbulent rotating magnetized plasma column

The turbulent regime of the rotating magnetized plasma column in the Mistral device has been studied. The structures inside the turbulence move on average along a spiral trajectory. These long-lived structures are convected in the background plasma to the walls contributing to a large extent both to particle and to energy transport. Without drift induced by the curvature and the gradient of the magnetic field, which is present only in curved devices, other mechanisms should occur in order to drive a radial convection of the structures. The detection and the spatiotemporal analysis of structures by means of conditional sampling techniques is performed. The conclusion is that the overall rotation and centrifugal effects lead to a net radial convection of the charged particles to the walls. The development of a poloidal electric field inside the structures is measured. From a theoretical point of view, our results show that centrifugal effects are important in driving turbulence in magnetized plasmas. This effect is rarely taken into account in existing numerical simulations of transport in fusion aimed devices. However, when fast shear layers exist in the edge of tokamaks, it can be an important contribution for the burst transport phenomenology.