The Study Of Jets With Kelvin-Helmholtz Vortexes Under Southward IMF Conditions

The Kelvin-Helmholtz(KH)instability is widespread in areas such as astro-physics,atomosphere,geophysics and applications in industries.Therefore,it is very important to study the mechanism of the KH instability.The Earth’s mag-netopause,which has large velocity shear,is an ideal place for KH instability to arise and develop.When the IMF is northward,the KH surface waves and vortices are frequently observed at the low latitude magnetopause,but the signatures of the magnetopause KH waves have been much less frequently observed during periods of the southward IMF.The main research contents and conclusions of this paper are as follows.1.We study the jet flows during the evolution of KH instability under pure southward IMF conditions.In the nonlinear phase,the KH vortex has a span of～12λnear the shear flow between magnetosphere and magnetosheath,with the duration of KH vortex～20t_Abefore decay,where t_Ais the typical time.The peak jet flows V_zcaused by the initial 3D system is about～0.5V_A.The obvious jet flows are distributed in both the spine region and the edge of the KH vortex,where the magnetic reconnection triggered by the KH instability.2.We study the evolution of KH instability and the process of multi-vortex coalescence under different magnetic fields.In a three-dimensional system,the evolution of KH instability is inhibited when there is a magnetic field component parallel to the shear layer.When there are magnetic field components in the KH plane,the jet flows will continue to grow larger after KH vortex merging and reach a peak value of about 1.0V_z.