Turbulence elasticity - A new mechanism for transport barrier dynamics

We present a new, unified model of transport barrier formation in " elastic" drift wave-zonal flow (DW-ZF) turbulence. A new physical quantity - the delay time (i.e., the mixing time for the DW turbulence) - is demonstrated to parameterize each stage of the transport barrier formation. Quantitative predictions for the onset of limit-cycle-oscillation (LCO) among DW and ZF intensities (also denoted as I-mode) and I-mode to high-confinement mode (H-mode) transition are also given. The LCO occurs when the ZF shearing (|〈v〉ZF′|) enters the regime Δωk<|〈V〉 ZF′|<τcr-1, where Δω_k is the local turbulence decorrelation rate and τ_cr is the threshold delay time. In the basic predator-prey feedback system, τ_cr is also derived. The I-H transition occurs when |〈V〉E×B′|>τ cr-1, where the mean E×B shear flow driven by ion pressure "locks" the DW-ZF system to the H-mode by reducing the delay time below the threshold value.