[P-EM30_1PO1] Plasma Astrophysics: turbulence, transport, nonlinear phenomenon

[PEM30-P02_1] The effect of the ion gyro motion to nonlinear processes of the Kelvin-Helmholtz instability

*Satoshi UENO¹, Takayuki UMEDA¹, Takuma NAKAMURA², Shinobu MACHIDA¹ (1.Solar-Terrestrial Environment Laboratory, 2.Los Alamos National Laboratory)

Keywords:the Kelvin-Helmholtz instability, Vlasov simulation, space plasma, nonlinear processes, secondary instabilities

Nonlinear evolution of the Kelvin-Helmholtz instability (KHI) at a transverse velocity shear layer in an inhomogeneous space plasma is investigated by means of a four-dimensional (two spatial and two velocity dimensions) electromagnetic Vlasov simulation. When the rotation direction of the primary KH vortex and the direction of ion gyro motion are same, there exists a strong ion cyclotron damping. In this case, spatial inhomogeneity inside the primary KH vortex is smoothed and the secondary Rayleigh-Taylor instability is suppressed. The ion gyro motion also suppresses the formation of secondary vortices in the spatial scale smaller than the ion gyro radius, when the rotation direction of the vortex and the direction of ion gyro motion are same. As a result, the secondary instabilities take place at different locations in the primary KH vortex, where the rotation direction of the secondary vortex and the direction of ion gyro motion are opposite. These results indicate that secondary instabilities occurring in the nonlinear stage of the primary KHI at the Earth's magnetospheric boundaries might show dawn-dusk asymmetries.