A generalized Ginzburg-Landau model for nonlinear relaxation oscillation of magnetized plasma boundary with shear flow
- Title
- A generalized Ginzburg-Landau model for nonlinear relaxation oscillation of magnetized plasma boundary with shear flow
- Authors
- YUN, GUNSU; OH, YOUNG MIN; LEE, Jieun; Hwang, Hyung Joo; LEE, Jaehyun; Leconte, Michael
- Date Issued
- 2017-10-23
- Publisher
- American Physical Society
- Abstract
- The boundary of high-temperature plasma confined by a toroidal magnetic field structure often undergoes quasi-periodic relaxation oscillations between high and low energy states. On the KSTAR tokamak, the oscillation cycle consists of a long quasi-steady state characterized by eigenmode-like filamentary modes, an abrupt transition into non-modal filamentary structure [Lee JE, {\it Sci. Rep.} 7, 45075], and its rapid burst (via magnetic reconnection) leading to the boundary collapse. A phenomenological model including the effects of time-varying perpendicular flow shear, turbulent transport, and external heating has been developed to understand the nonlinear oscillation. The model, which has the form of a generalized complex Ginzburg-Landau equation, shows that the flow shear amplitude and the shear layer width determine the nonlinear oscillation. Numerical solutions revealed that there exists a critical flow shear level below which steady states can exist. This result suggests that the abrupt transition to the non-modal unstable state is due to the flow shear increasing above the critical level. The model predicts that high wavenumber (k) modes can coexist with low-k modes at sufficiently low level of flow shear [Lee J, {\it Phys. Rev. Lett.} 117, 075001].
- URI
- https://oasis.postech.ac.kr/handle/2014.oak/45745
- Article Type
- Conference
- Citation
- 59th Annual Meeting of the APS Division of Plasma Physics, page. CP11 - 00126, 2017-10-23
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