(TH/P8-17) Multi-scale Transport Dynamics Dominated by Multiple Dissipation Mechanisms near the Critical Gradient
1) Kyoto University, Uji, Japan
2) Japan Atomic Energy Agency, Naka, Ibaraki-ken 311-0193, Japan
3) Department of Applied Mathematics, University of Sheffield, S3 7RH, UK
* Present address: University of California, San Diego, La Jolla, California, USA
We found a new class of transient transport near the critical gradient (CG) referred to as GAM growing intermittency , which is caused by the collision-less GAM damping and leads to dynamical establishment of the Dimits shift. Here, we present a new predator-prey model which includes the effect of anisotropic pressure perturbation (GAM) and parallel ion sound velocity and successfully reproduces the essential features of the growing intermittency. We have also extended the simulation model by taking into account the collisional zonal flow (ZF) damping. Due to the mixture of two kinds of damping mechanisms, i.e., the GAM damping and collisionnal damping, the growing intermittency is found to recursively appear accompanied with complex envelope modulation to ZFs over collisional (or transport) time scale. Furthermore, we have investigated the effect of zonal pressure (ZP) near the CG, which also works as a dissipation mechanism. The ZP changes the temperature scale length through the coupling with GAMs and causes a sudden termination of the growing intermittency. Thus, the multiple dissipation mechanisms are found to synergetically couple each other and lead plasmas to complex dynamical transport over long time scale.
 K. Miki etal. Phys. Rev. Lett. 99, 145003 (2007).
Full paper available (PDF)