Three-dimensional MHD models for the interaction between the solar wind and the interstellar medium

We attempted to perform, a global three-dimensional (3-D) MHD computer simulation of the outer heliosphere under the interaction of the solar wind plasma with the interstellar medium, and showed that MHD processes are important in analyzing 3-D global heliospheric structure. The magnetic pressure effect of the interplanetary spiral field, which has been discussed theoretically and analyzed by a 2-D simulation, was examined in detail in our 3-D global system. The contraction of the scale of the terminal shock due to the magnetic pressure effect was analyzed quantitatively. It was found that in the downstream side of the interstellar flow, the magnetic pressure force contracts the scale of the terminal shock more evidently, which produces an isotropic structure of the shock rather than a bullet-type shape which was obtained by a hydrodynamic simulation. Collimated polar streams of the solar wind due to the magnetic pressure are also found in the heliosheath. In addition, the magnetic pressure is found to make the sheet plasma more dominant along the equatorial disk in the heliosheath.