Test Particle Simulation of Solar Wind Transport into the Magnetosphere during Northward IMF

Using test particle method, with the background fields obtained from a global Magnetohydrodynamics (MHD) simulation driven by the ACE satellite observation data, the transport process of solar wind particles into the Earth’s magnetosphere was simulated during a long-term northward Interplanetary Magnetic Field (IMF) event on 22－24 October 2003. The particle density distribution in the magnetosphere and the time evolution characteristics of the particles were analyzed and discussed. During the northward IMF, the particle density in the dawn-side ring current region is higher than that on the dusk side, and the radial range on the dawn side is wider. The magnetosheath particles on the tail side can transport into magnetosphere through the low-latitude boundary layer, but they are difficult to enter into magnetosphere through the north and south magnetopause. The solar wind particles transported into the nightside magnetosphere gather to form a Cold Dense Plasma Sheet (CDPS). The spatial scale and particle density of the CDPS obtained from the simulation are consistent with observations. During the long-term northward IMF period, the total number of particles in the magnetotail showed a trend of increasing over time. At the same time, there exists a weak quasi-periodic variation with a period of about 20 min and a strong quasi-periodic variation with a period of about 5～6 h.