@article{oai:repo.qst.go.jp:00079219,
 author = {Wang, Wei and Kishimoto, Yasuaki and Imadera, Kenji and Liu, Hairui and Li, Jiquan and Yagi, Masatoshi and Wang, Zhengxiong and Wang, Wei and Yagi, Masatoshi},
 issue = {6},
 journal = {Nuclear Fusion},
 month = {Mar},
 note = {Flux-driven ion temperature gradient (ITG) turbulence and associated transport regulated by non-local and non-diffusive processes are investigated based on GKNET simulations in a global toroidal geometry. Among these processes, the instantaneous formation of radially extended quasi-coherent structure, which leads to the transport burst, is found to play an important role in causing global profile formation and relaxation. To elucidate the characteristics of such a transport process, we introduce the size probability distribution function (size-PDF) P(S) to analyze heat flux eddies in the real space, with S the eddy size, incorporated with Fourier-based approaches in spectral space. In the size-PDF to the quiescent phase, P(S) is found to be fitted by three piecewise power laws which transitions at two typical sizes S_a and S_b as P∝S^(-2/3)  (S≤S_a), P∝S^(-2) (S_a≤S≤S_b), and P∝S^(-4)  (S≥S_b), where S_a~50 and S_b~200 in squared gyro-radius unit ρ_i^2 for the system with a⁄ρ_i ~225 (a: the minor radius). On the other hand, the size-PDF in the bursting phase exhibits non-power law irregular humps corresponding to the quasi-coherent structure for S≥S_b reaching to S~1500. Such a coherent structure is ascribed to the spontaneous alignment of smaller scale eddies through phase matching in radial direction, which is classified as a quasi-deterministic process. Resultantly, a large amount of free energy is extracted from the system due to subsequent growth of the event, by which a self-organized profile is established. The coherent structure is then readily disintegrated by self-generated zonal flows, so that the energy is transferred to smaller eddies, by which the quasi-probabilistic transport including SOC type avalanche is induced on the profile. To conclude, the transport is found to be regulated by the mixture of a quasi-deterministic and a probabilistic process, which leads to stiffness and resilience in the profile formation and self-similarity in the relaxation.},
 title = {Statistical study for ITG turbulent transport in flux-driven tokamak plasmas based on global gyro-kinetic simulation},
 volume = {60},
 year = {2020}
}