Magnetic reconnection induced by the Kelvin-Helmholtz vortex at the Earth's magnetopause during southward IMF

When the interplanetary magnetic field (IMF) is strongly northward or southward, the magnetic field component parallel to the shearing flow across the Earth's low-latitude magnetopause is small, and this allows the flow to satisfy the super-Alfvénic unstable condition for the Kelvin-Helmholtz instability (KHI) along the low-latitude magnetopause. This process has long been believed as a key candidate for causing the anomalous solar wind transport into the magnetosphere especially during the northward IMF, since clear signatures of the KH waves have been frequently observed during the northward IMF. However, these signatures of the KH waves have been much less frequently observed during the southward IMF, and therefore the role of the KHI during the southward IMF is still unclear. Here, we performed a first 3D fully kinetic simulation of the KHI at the magnetopause under the southward IMF condition. The simulation demonstrates that magnetic reconnection, which evolves in the direction perpendicular to the vortex layer, is driven at multiple points within the vortex, leading to a rapid destruction of the vortex structure. This turbulent process also causes an efficient solar wind transport across the magnetopause. These results indicate (i) that the rapid destruction of the vortex structure can make it hard to identify the KH waves by in-situ observations during the southward IMF, and (ii) that the KH waves may play an important role in transferring the solar wind into the magnetosphere even during the southward IMF.