Hemispheric and dawn-dusk asymmetries of Kelvin-Helmholtz waves and magnetic reconnection caused by dipole tilt and IMF By

Along with magnetic reconnection, Kelvin-Helmholtz (KH) waves are the main mechanisms controlling the solar wind-magnetosphere interaction. Kelvin-Helmholtz waves have been shown to be important for plasma transport into the magnetosphere, enabled by secondary processes such as reconnection, diffusion and wave-particle interactions. In this paper we use magnetohydrodynamical (MHD) simulations for studying how the Kelvin-Helmholtz instability (KHI) is modulated by the dipole tilt angle and IMF $B_y$. We find that KH wave activity on the magnetopause maximizes in the winter hemisphere and at dawn sector for positive IMF $B_y$. These asymmetries of KHI are caused by asymmetric draping of interplanetary magnetic field (IMF) in the magnetosheath and dawn-dusk asymmetry in magnetic reconnection, creating a broader boundary layer slowing the growth of KHI at dusk for positive $B_y$. These results are important, e.g., for understanding field-aligned currents generated by the KH vortices and their ionospheric effects during different seasons and IMF conditions.