title: Mean and oscillating plasma flows and turbulence interactions across the L-H confinement transition.
abstract: A complex interaction between turbulence driven E × B zonal flow oscillations, i.e., geodesic acoustic modes (GAMs), the turbulence, and mean equilibrium flows is observed during the low to high (L-H) plasma confinement mode transition in the ASDEX Upgrade tokamak. Below the L-H threshold at low densities a limit-cycle oscillation forms with competition between the turbulence level and the GAM flow shearing. At higher densities the cycle is diminished, while in the H mode the cycle duration becomes too short to sustain the GAM, which is replaced by large amplitude broadband flow perturbations. Initially GAM amplitude increases as the H-mode transition is approached, but is then suppressed in the H mode by enhanced mean flow shear.
authors.affiliation: EURATOM-Association IPP, Max-Plank-Institut für Plasmaphysik, D-85748, Garching, Germany.
authors.forename: G D
authors.initials: GD
authors.lastname: Conway
authors.forename: C
authors.initials: C
authors.lastname: Angioni
authors.forename: F
authors.initials: F
authors.lastname: Ryter
authors.forename: P
authors.initials: P
authors.lastname: Sauter
authors.forename: J
authors.initials: J
authors.lastname: Vicente