Striking features of the Alfven Transition Layer in the Magnetic Cusp region; 3D Global PIC Simulation

The solar-terrestrial magnetosphere interaction is analyzed by using a global 3D PIC simulation, with a special focuss on the 3D magnetic cusp region. Our recent global simulation results (Cai et al., JGR, 2015), have analyzed in details the main features of the magnetic cusp under a northward Interplanetary Magnetic Field (IMF) configuration; these have been compared with the three-year statistical observations of Cluster satellites (Lavraud and al., JGR, 2005), and with the previous MHD simulation results, in order to complete the update global view of the magnetic cusp that MHD model cannot obtain. One important feature is the evidence of the Alfven Transition Layer (ATL) where Ma 0, almost adjacent to the upper edge of the stagnant exterior cusp (SEC), whose width varies from 1 -4 Re around the magnetopause. Through the ATL, the plasma flow transits from super- to sub-Alfvenic regime from the magnetosheath to SEC. Present results evidence (i) the asymmetric complicated 3D topology of the ATL, and (ii) the presence of a depletion region within the ATL, where both ions and electrons enter into the cusp region. These features are analyzed as the IMF varies from northward to southward through dawn-dusk-ward configuration in order to analyze how the deformation of the ATL region may affect the particle entry into the cusp region. Using four MMS tetrahedral data, the ATL surface can be tessellated using the marching cube algorithm. Results will be discussed for possible comparison with MMS data.