Nonlinear evolution of the Kelvin-Helmholtz instability in the double current sheet configuration

Journal Article · Tue Mar 15 00:00:00 EDT 2016 · Physics of Plasmas

DOI:https://doi.org/10.1063/1.4943888· OSTI ID:22599023

Mao, Aohua ^[1]; Li, Jiquan; Kishimoto, Yasuaki ^[2]; Liu, Jinyuan ^[3]

---

1. Laboratory for Space Environment and Physical Sciences, Harbin Institute of Technology, Harbin 150001 (China)
2. Graduate School of Energy Science, Kyoto University, Gokasho, Uji, Kyoto 611-0011 (Japan)
3. School of Physics and Optoelectronic Technology, Dalian University of Technology, Dalian 116000 (China)

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.

• OSTI ID: 22599023
• Journal Information: Physics of Plasmas, Vol. 23, Issue 3; Other Information: (c) 2016 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA); ISSN 1070-664X
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
71 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