Unveiling the Mixing and Transport Processes of Solar Wind and Planetary Ions in the Magnetopause Boundary Layer

Abstract

Kelvin-Helmholtz (KH) vortices are widely observed in astrophysics and heliophysics, including at Jovian and terrestrial magnetopauses, the Martian sheath-ionosphere boundary, the heliopause, and within stellar accretion disks. These vortices play a critical role in transporting mass, momentum, and energy across boundary layers. Magnetized planets such as Earth exhibit a higher incidence of fully rolled-up, nonlinear KH vortices compared to non-magnetized planets like Mars. In contrast to previous magnetohydrodynamic (MHD) studies, this work adopts a kinetic point of view to quantify ion mixing rates using three-dimensional global hybrid simulations, with Earth as a representative case. This approach enables automated identification of the KH-modulated, corrugated magnetopause. For the first time, we provide a quantitative assessment of how solar wind conditions control solar wind entry and subsequent mixing with magnetospheric ions via KH waves. We find that under northward interplanetary magnetic field (IMF) conditions, the flux of particles crossing the dayside magnetopause increases with solar wind dynamic pressure and peaks in the KH region. Notably, the KH-modulated low-latitude boundary layer thins as the dynamic pressure increases. Under southward IMF conditions, coupled reconnection and KH structures further enhance solar wind injection and boost magnetospheric ion escape in the dayside, especially near the subsolar point where reconnection intensifies this exchange. These results also shed light on the evolution of space environments and mass transport at magnetized planets in the heliosphere and beyond.