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Author Mao, Aohua ♦ Li, Jiquan ♦ Kishimoto, Yasuaki ♦ Liu, Jinyuan
Source United States Department of Energy Office of Scientific and Technical Information
Content type Text
Language English
Subject Keyword PLASMA PHYSICS AND FUSION TECHNOLOGY ♦ CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS ♦ AMPLITUDES ♦ CONFIGURATION ♦ EQUILIBRIUM ♦ FLUCTUATIONS ♦ HELMHOLTZ INSTABILITY ♦ MAGNETIC ISLANDS ♦ MAGNETIC RECONNECTION ♦ MAGNETIC SURFACES ♦ MATHEMATICAL EVOLUTION ♦ NONLINEAR PROBLEMS ♦ PLASMA ♦ PLASMA SIMULATION ♦ SHEAR ♦ SHEETS ♦ STEADY-STATE CONDITIONS ♦ TEARING INSTABILITY ♦ TURBULENCE ♦ VORTEX FLOW ♦ VORTICES
Abstract The nonlinear evolution of the Kelvin-Helmholtz (KH) instability driven by a radially antisymmetric shear flow in the double current sheet configuration is numerically investigated based on a reduced magnetohydrodynamic model. Simulations reveal different nonlinear fate of the KH instability depending on the amplitude of the shear flow, which restricts the strength of the KH instability. For strong shear flows far above the KH instability threshold, the linear electrostatic-type KH instability saturates and achieves a vortex flow dominated quasi-steady state of the electromagnetic (EM) KH turbulence with large-amplitude zonal flows as well as zonal fields. The magnetic surfaces are twisted significantly due to strong vortices but without the formation of magnetic islands. However, for the shear flow just over the KH instability threshold, a weak EM-type KH instability is saturated and remarkably damped by zonal flows through modifying the equilibrium shear flow. Interestingly, a secondary double tearing mode (DTM) is excited subsequently in highly damped KH turbulence, behaving as a pure DTM in a flowing plasma as described in Mao et al. [Phys. Plasmas 21, 052304 (2014)]. However, the explosive growth phenomenon is replaced by a gradually growing oscillation due to the extremely twisted islands. As a result, the release of the magnetic energy becomes slow and the global magnetic reconnection tends to be gentle. A complex nonlinear interaction between the EM KH turbulence and the DTMs occurs for the medium shear flows above the KH instability threshold, turbulent EM fluctuations experience oscillatory nonlinear growth of the DTMs, finally achieves a quasi-steady state with the interplay of the fluctuations between the DTMs and the EM KH instability.
ISSN 1070664X
Educational Use Research
Learning Resource Type Article
Publisher Date 2016-03-15
Publisher Place United States
Journal Physics of Plasmas
Volume Number 23
Issue Number 3


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