Kelvin-Helmholtz instability for a bounded plasma flow in a longitudinal magnetic field

T. Burinskaya (1) , M. Shevelev (1) , Jean-Louis Rauch (2)

1 IKI - Space Research Institute of the Russian Academy of Sciences
2 LPC2E - Laboratoire de Physique et Chimie de l'Environnement et de l'Espace

Kelvin-Helmholtz MHD instability in a plane three-layer plasma is investigated. A general dispersion relation for the case of arbitrarily orientated magnetic fields and flow velocities in the layers is derived, and its solutions for a bounded plasma flow in a longitudinal magnetic field are studied numerically. Analysis of Kelvin-Helmholtz instability for different ion acoustic velocities shows that perturbations with wavelengths on the order of or longer than the flow thickness can grow in an arbitrary direction even at a zero temperature. Oscillations excited at small angles with respect to the magnetic field exist in a limited range of wavenumbers even without allowance for the finite width of the transition region between the flow and the ambient plasma. It is shown that, in a low-temperature plasma, solutions resulting in kink-like deformations of the plasma flow grow at a higher rate than those resulting in quasi-symmetric (sausage-like) deformations. The transverse structure of oscillatory-damped eigenmodes in a low-temperature plasma is analyzed. The results obtained are used to explain mechanisms for the excitation of ultra-low-frequency long-wavelength oscillations propagating along the magnetic field in the plasma sheet boundary layer of the Earth’s magnetotail penetrated by fast plasma flows.

Domains: Plasma Physics [physics.plasm-ph]; Space Physics [physics.space-ph]

T. Burinskaya, M. Shevelev, Jean-Louis Rauch. Kelvin-Helmholtz instability for a bounded plasma flow in a longitudinal magnetic field. Fizika Plazmy / Plasma Physics Reports, 2011, 37 (1), pp.43-55. ⟨10.1134/S1063780X10111029⟩. ⟨insu-02507698⟩