3D Full particle simulations of the solar wind-terrestrial magnetosphere interaction: impact of the IMF rotation on the dipolarization process of magnetospheric dynamics

A large scale three-dimensional global PIC simulations are performed in order to analyze the dynamics of the magnetotail as the interplanetary magnetic field (IMF) rotates from northward to southward direction (Figs 1 and 2). This dynamics reveals to be quite different within meridan/equatorial planes over two successive phases of this rotation. First, as IMF rotates from North to Dawn-Dusk direction, the X-Point (magnetic reconnection) evidenced in the magnetotail (meridian plane) is moving earthward (from x=-35 Re to x=-17.5) distance at which it stabilizes. This motion is coupled with the formation of "Crosstail-S" patterns (within the plane perpendicular to the Sun-Earth line) through the neutral sheet in the nearby magnetotail. Second, as IMF rotates from dawn-dusk to South, the minimum B field region is expanding within the equatorial plane and forms a ring. This two-steps dynamics is analyzed in strong association with the cross-field magnetotail current Jy, in order to recover the signatures of substorms triggering. The second step dynamics is complex and can be classified into two-phases because there is a significant delay in the penetration of the IMF into the magnetotail. In the first phase in the second step, Jy in the magnetotail disappears. After the dipolarization, IMF penetrates into the magnetotail region and Jy appears again in the second phase. In addition, we use the so-called Alfven Transition Layer (ATL) where Alfven Mach number is nearly zero to investigate how the magnetosphere response to the IMF rotations related to the dipolarization process.