Global MHD Simulation Of Interaction Between Interplanetary Shocks And Magnetosphere

This paper presents global magnetohydrodynamic (MHD) simulations of the solar wind-magnetosphere-ionosphere system, and discusses in turn the treatment of the ionosphere, the structure of the steady magnetosphere, the interaction between interplanetary (IP) shocks and the magnetosphere, and the response of the ionosphere to such interaction. The simulation results are compared with relevant observations.We use spherical shell approximation and electrostatic description and take a uniform Pedersen conductivity and zero Hall conductivity for the ionosphere. The magnetosphere provides the field-aligned current (FAC) as the source for the ionospheric electric field. Solving the elliptic equation of the ionospheric potential, we obtain the potential distribution in the ionosphere generated by the FAC. The distribution of potential is then mapped to the inner magnetosphere so as to induce an electric field drift and to drive the magneto-spheric convection. The Fourier transformation and the push-pull method are combined in solving the equation of ionospheric potential. The numerical code is tested by a simple example in which the numerical solution agrees well with the corresponding analytical solution.Combining the ionosphere-magnetosphere coupling model with a recently developed PPMLR-MHD code for the global simulation of the magnetosphere, we carried out numerical simulations in order to model the large-scale structure of the quasi-steady magnetosphere and ionosphere. Simulations are made for both due northward and due southward IMF cases, resulting in numerical solutions of steady magnetosphere and distributions of ionospheric potential. For the due northward IMF case, the Earth's magnetic field is completely closed, magnetic reconnection takes place in the tailward neighborhood of the cusp regions, and multiple convection vortices appear in the ionosphere. For the due southward IMF case, on the other hand, the Earth's magnetic field is partly opened, magnetic reconnection occurs in the day side magnetopause and the magnetotail, and a typical double convection vortex appears in the ionosphere. The structures of the magnetosphere are remarkably different in the two IMF cases. These results agree essentially with previous ones obtained by either qualitative estimations or numerical simulations.In order to simulate the dynamical response of the magnetosphere-ionosphere system to IP shocks we take a steady solution with Parker's spiral field (B_z=0) for the IMF...