Fluctuation level bursts in a model of internal transport barrier formation

A model of internal transport barriers (ITB) is developed that, in addition to the typical features of ITB models (the phase transition character with a power threshold, barrier front propagation, etc.), exhibits an oscillatory/bursty behavior close to the transition. This behavior comes from the competition between the driving and suppression mechanisms for the turbulence. The onset of the oscillations has a power threshold, Posc, below the power threshold for the transition to the enhanced confinement regime, Pth. In the calculations, Posc∼0.5Pth. This suggests that the oscillations avoid an early transition at Pth=Posc, so any mechanism that eliminates the oscillations may lower the transition power.