The generation dynamics and the structural characteristics of zonal flows are investigated in the double tearing mode (DTM) with antisymmetric shear flows. Two kinds of zonal flow oscillations are revealed based on reduced resistive magnetohydrodynamics simulations, which depend on the shear flow amplitudes corresponding to different DTM eigen mode states, elaborated by Mao et al. [Phys. Plasmas 20, 022114 (2013)]. For the weak shear flows below an amplitude threshold, vc, at which two DTM eigen states with antisymmetric or symmetric magnetic island structure are degenerated, the zonal flows grow oscillatorily in the Rutherford regime during the nonlinear evolution of the DTMs. It is identified that the oscillation mechanism results from the nonlinear interaction between the distorted islands and the zonal flows through the modification of shear flows. However, for the medium shear flows above vc but below the critical threshold of the Kelvin-Helmholtz instability, an oscillatory growing zonal flow occurs in the linear phase of the DTM evolution. It is demonstrated that the zonal flow oscillation originates from the three-wave mode coupling or a modulation instability pumped by two DTM eigen modes with the same frequency but opposite propagating direction. With the shear flows increasing, the amplitude of zonal flow oscillation increases first and then decreases, whilst the oscillation frequency as twice of the Doppler frequency shift increases. Furthermore, impacts of the oscillatory zonal flows on the nonlinear evolution of DTM islands and the global reconnection are also discussed briefly.
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May 2014
Research Article|
May 09 2014
Zonal flow dynamics in the double tearing mode with antisymmetric shear flows
Aohua Mao;
Aohua Mao
1
School of Physics and Optoelectronic Technology, Dalian University of Technology
, Dalian 116024, China
2Graduate School of Energy Science,
Kyoto University
, Uji, Kyoto 6110011, Japan
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Jiquan Li;
Jiquan Li
a)
2Graduate School of Energy Science,
Kyoto University
, Uji, Kyoto 6110011, Japan
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Jinyuan Liu;
Jinyuan Liu
b)
1
School of Physics and Optoelectronic Technology, Dalian University of Technology
, Dalian 116024, China
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Yasuaki Kishimoto
Yasuaki Kishimoto
2Graduate School of Energy Science,
Kyoto University
, Uji, Kyoto 6110011, Japan
3
Institude of Advanced Energy, Kyoto University
, Uji, Kyoto 6110011, Japan
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a)
Electronic mail: [email protected]
b)
Electronic mail: [email protected]
Phys. Plasmas 21, 052304 (2014)
Article history
Received:
February 28 2014
Accepted:
April 28 2014
Citation
Aohua Mao, Jiquan Li, Jinyuan Liu, Yasuaki Kishimoto; Zonal flow dynamics in the double tearing mode with antisymmetric shear flows. Phys. Plasmas 1 May 2014; 21 (5): 052304. https://doi.org/10.1063/1.4875729
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