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The Global Structure of the Heliosphere

Abstract:

As the Sun moves through the local interstellar medium (LISM), it emits charged particles, creating the heliosphere occupied by the plasma of solar origin. Determining the structure of the heliosphere is a fundamental question that can be answered only by numerical simulations based on sophisticated theoretical models. Apart from the physics involved in the interaction of fully ionized, collisionless solar wind (SW) with the partially ionized, weakly collisional LISM, it is natural for humankind to speculate about our place of habitat as seen from a distance. This is especially germane now in light of recently observed astrospheres that possess substantially different shapes and structures. We present simulations of the SW-LISM interaction in a very large computational box, paying specific attention to modifications of the LISM properties caused by the presence of the heliosphere. Our results show that the heliosphere has a long heliotail, whose morphology is affected by the interstellar magnetic field pressure, so it acquires a sheetlike shape oriented along the plane formed by the interstellar magnetic field and velocity vectors in the unperturbed LISM. The SW-LISM boundary is subject to instabilities. A possibility is demonstrated of a quasi-parallel, slow-mode bow shock that affects some parts of the LISM flow. We demonstrate that the complex heliospheric structure affects the distribution of plasma and magnetic field in the LISM, resulting in a Galactic cosmic ray anisotropy consistent with the Tibet air shower experiment. We also analyze the effect of turbulence on the length of the heliotail and its ultimate destruction.