Nonlinear interaction between double tearing mode and Kelvin-Helmholtz instability with different shear flows

Area of Science:

• Plasma Physics
• Magnetohydrodynamics (MHD)
• Instability Theory

Background:

• Double tearing modes (DTMs) and Kelvin-Helmholtz (KH) instabilities are crucial phenomena in plasma dynamics.
• Understanding their nonlinear interaction is vital for astrophysical and fusion energy research.
• Previous studies have explored these instabilities separately or in different plasma regimes.

Purpose of the Study:

• To numerically investigate the nonlinear interaction between DTMs and KH instabilities.
• To examine this interaction in plasmas with weak and reversed magnetic shear profiles.
• To elucidate the role of magnetic shear in the formation of high-mode harmonics and nonlinear reconnection.

Main Methods:

• Utilized a compressible magnetohydrodynamics (MHD) model for numerical simulations.
• Focused on plasmas with weak and reversed magnetic shear, considering the stabilizing effect of field line bending.
• Analyzed the dynamics of coupled DTM-KH instabilities under different shear flow profiles.

Main Results:

• KH instabilities were found to couple with DTMs in weak and reversed magnetic shear plasmas.
• The KH mode was observed to dominate the instability dynamics.
• Weak magnetic shear was identified as crucial for the generation of high-mode harmonics.
• Symmetric flows led to asymmetric forced magnetic reconnection, causing mode interlocking.

Conclusions:

• The KH instability plays a dominant role in the nonlinear interaction with DTMs in specific plasma conditions.
• Weak magnetic shear is a critical factor in the development of complex instability dynamics and harmonic generation.
• This research enhances the understanding of nonlinear magnetic reconnection mechanisms relevant to astrophysics and fusion energy.