Abstract: How solar wind plasma enters the Earth’s magnetosphere when the interplanetary magnetic field (IMF) is northward is an active research topic.To further demonstrate that the Kelvin‒Helmholtz instability (KHI) is the main mechanism by which particles of the solar wind enter Earth’s magnetosphere , we use numerical simulation methods to study the motion of magnetic flux tubes at the Earth’s magnetospheric flanks. These magnetic flux tubes are obtained through conjugate reconnection in the nonlinear stage of the KHI. The part of the original magnetic flux tube of the magnetosphere near the equator was replaced by a part of the magnetic flux tube of the magnetosheath. The reconnected magnetic flux tube, which contains a large number of magnetosheath particles, forms a low-entropy magnetic flux tube.The simulation results indicate that the reconnected magnetic flux tube flows toward the Sun along the magnetospheric flanks. This is consistent with the sunward flow in the center of the polar cap under northward IMF conditions. Analysis of the internal parameters of the flowing magnetic flux tube reveals that the newborn magnetic flux tube contributes to the formation of a cold and dense plasma sheet.