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Kawai, Chika*; Idomura, Yasuhiro; Ogawa, Yuichi*; Yamada, Hiroshi*
Physics of Plasmas, 27(8), p.082302_1 - 082302_11, 2020/08
Times Cited Count：1 Percentile：6.31(Physics, Fluids & Plasmas)Self-organization in the toroidal electron temperature gradient driven (ETG) turbulence is investigated based on a global gyrokinetic model in a weak magnetic shear configuration. Because of global profile effects, toroidal ETG modes with higher toroidal mode number n are excited at the outer magnetic surfaces, leading to strong linear wave dispersion. The resulting anisotropic wave turbulence boundary and the inverse energy cascade generate the self-organization of zonal flows, which is the unique mechanism in the global gyrokinetic model. The self-organization is confirmed both in the decaying turbulence initialized by random noises and in the toroidal ETG turbulence. It is also shown that the self-organization process generates zonal flows and isotropic eddies depending on a criterion parameter, which is determined by the ion to electron temperature ratio and the turbulence intensity.
Kawai, Chika*; Idomura, Yasuhiro; Maeyama, Shinya*; Ogawa, Yuichi*
Physics of Plasmas, 24(4), p.042303_1 - 042303_13, 2017/04
Times Cited Count：2 Percentile：10.61(Physics, Fluids & Plasmas)Self-organization in the slab electron temperature gradient driven (ETG) turbulence is investigated based on gyrokinetic simulations and the Hasegawa-Mima (HM) equation. The scale and the anisotropy of self-organized turbulent structures vary depending on the Rhines scale and the characteristic scale given by the adiabatic response term in the HM equation. The former is determined by competition between the linear wave dispersion and the nonlinear turbulent cascade, while the latter is given as the scale, at which the turbulent cascade is impeded. These scales are controlled by plasma parameters such as the density and temperature gradient, and the temperature ratio of ion to electron. It is found that depending on the plasma parameters, the ETG turbulence shows either isotropic turbulence or zonal flows, which give significantly different transport levels. Although the modulational instability excites zonal modes regardless of the plasma parameters, the final turbulent structure is determined by the self-organization process.
Kishimoto, Yasuaki
Purazuma, Kaku Yugo Gakkai-Shi, 80(5), p.390 - 395, 2004/05
High performance magnetically confined plasma is realized by having structures in plasmas, where different elementary processes with different time and spatial scales are deeply contributing with each other. A research based on large scale simulation is then essential to understand such hierarchical complex plasmas. We discuss the underlying physical process of the structural plasma and present a prospect for future numerical simulations covering a wide dynamical range.
Li, J.; Kishimoto, Yasuaki
Physics of Plasmas, 11(4), p.1493 - 1510, 2004/04
Times Cited Count：58 Percentile：85.33(Physics, Fluids & Plasmas)The electron temperature gradient (ETG) driven turbulence in tokamak core plasmas is numerically investigated based on three-dimensional gyrofluid model with adiabatic ion response. Attentions are focused on the zonal flow dynamics in ETG fluctuations and the resultant electron heat transport. A high electron energy confinement mode is found in the weak magnetic shear regime, which is closely relevant with self-organization behavior of turbulence through the enhanced zonal flow dynamics rather than the weak shear stabilization of ETG fluctuations. It is demonstrated that the weak shear is favorable for the enhancement of zonal flows in ETG turbulence.
Suzudo, Tomoaki
Lecture Notes in Computer Science 3305, p.151 - 160, 2004/00
This paper discuss a class of 2-dimensional asynchronous cellular automata with conservation of mass, for the formation of patterns in groups. The previous study reported a methodology of searching, automatically, for pattern-forming cellular automata using a genetic algorithm; this approach successfully found a few types of pattern-forming rules. The current study is a series of statistical analyses of one of the classes found by the above methodology, with the hope of understanding the mechanisms of the pattern formation. These analyses lead to some basic logic necessary to the pattern formation, but not to enough information to elucidate the whole mechanism of the pattern formation. This result suggests that the existence of unidentified cooperative operations between the different transitions of the cellular automaton rule to carry out the pattern formation.
Kishimoto, Yasuaki
Purazuma, Kaku Yugo Gakkai-Shi, 79(5), p.460 - 463, 2003/05
This is a collection of review article related to the "Multiple Time and Spatial Scale Plasma Simulation" of various fields including fundamental research area of self-organization, magnetic and laser fusion field, space and astrophysics field where a plasma plays an essential roles.
on MgO(100)Vacik, J.; Naramoto, Hiroshi; Narumi, Kazumasa; Yamamoto, Shunya; Miyashita, Kiyoshi*
Journal of Chemical Physics, 114(20), p.9115 - 9119, 2001/05
Times Cited Count：20 Percentile：53.87(Chemistry, Physical)no abstracts in English
and Ni on the MgO(100) single crystalVacik, J.; Naramoto, Hiroshi; Narumi, Kazumasa; Yamamoto, Shunya; Miyashita, Kiyoshi*
Materials Research Society Symposium Proceedings, Vol.648, p.P3.50.1 - P3.50.6, 2001/00
None
*; *
Journal of the Physical Society of Japan, 67(12), p.4302 - 4303, 1998/12
Times Cited Count：7 Percentile：51.28(Physics, Multidisciplinary)no abstracts in English
*; *
Journal of the Physical Society of Japan, 67(2), p.441 - 450, 1998/02
Times Cited Count：11 Percentile：60.62(Physics, Multidisciplinary)no abstracts in English
Kishimoto, Yasuaki; Tajima, Toshiki*; W.Horton*; LeBrun, M. J.*; J.Y.Kim*
Physics of Plasmas, 3(4), p.1289 - 1307, 1996/04
Times Cited Count：79 Percentile：89.55(Physics, Fluids & Plasmas)no abstracts in English
; Suzuki, Katsuo; Fujii, Yoshio; Shinohara, Yoshikuni
JAERI-M 89-191, 25 Pages, 1989/11
no abstracts in English
Kawai, Chika; Maeyama, Shinya; Idomura, Yasuhiro; Ogawa, Yuichi*
no journal, ,
Self-organization through inverse cascades of energy in a turbulent spectrum is considered as one of the paths to formation of zonal flow structures in magnetized plasma. Despite the theoretical suggestion, relations between the turbulence energy spectrum and the formation of zonal flow structures have not been rigorously investigated in terms of numerical simulation studies based on a first-principle model. In this study, spectrum structures of electron scale plasma turbulence are obtained from high-resolution Vlasov simulations. The long wave length region of the spectrum is investigated in relation with self-organization.
Kawai, Chika; Idomura, Yasuhiro; Maeyama, Shinya; Ogawa, Yuichi*
no journal, ,
In estimating confinement properties of fusion plasmas, it is a critical issue to understand structures of turbulent spectra, leading to turbulent transport. In this study, self-organization processes, which produce zonal flows from electron turbulence, are analyzed in detail via a highly accurate gyrokinetic Eulerian code, and structures of turbulent spectra leading to zonal flow generation are clarified.
Kawai, Chika; Idomura, Yasuhiro; Maeyama, Shinya*; Ogawa, Yuichi*
no journal, ,
To investigate relations between self-organization and flow structure formation in magnetized plasmas, energy spectrum structures of electron turbulence are estimated by gyrokinetic simulations. It is found that the existence of zonal flow formation is affected by the plasma density and the temperature ratio between ions and electrons, which change wave dispersion induced by diamagnetic rotation. Depending on saturation amplitudes of turbulence, zonal flow formation processes are varied from an inverse energy cascade due to self-organization to a modulational instability due to direct mode coupling. These results suggest that structures of electron turbulence are significantly changed by macroscopic plasma parameters.
Idomura, Yasuhiro
no journal, ,
Fusion plasma turbulence often shows self-organized turbulent structures such as zonal flows. This phenomenon has been is discussed by analogy with a self-organization picture described by the Hasegawa-Mima (H-M) equation. Although the H-M equation predicts several important features such as the dual cascade of turbulent spectra, the Rhines scale, and the adiabatic response scale, these basic features have not examined in fusion plasma turbulence so far. In this talk, we present the self-organization of electron temperature gradient driven turbulence, examine these basic features, and discuss their impact on turbulent transport.
