Surprises From The Edge Of The Solar System: Voyager At The Final Frontier
Abstract
Our solar system presents a unique local example of the interaction of a stellar wind and the interstellar medium. As the Sun travels through the interstellar medium, it is subject to an interstellar wind. The heliosphere is created by the supersonic solar wind that abruptly slows, forming a termination shock as it approaches contact with the interstellar medium at the heliopause. After 27 years of anticipation, in 2004 December 16, Voyager 1, crossed the termination shock, at 94AU, and began exploring the heliosheath. The twin Voyager spacecraft are probing the northern and southern hemispheres of the heliosphere. Voyager 1 is now beyond 98AU, while Voyager 2 is beyond 78 AU. As Voyager 1 crossed the termination shock, and began exploring the heliosheath it became increasingly clear that this previously unexplored region is full of surprises. These include the startling absence of the anomalous cosmic ray source that had been widely anticipated, the unusually slow and even sunward flow of the solar wind in the heliosheath, and the unexpected direction of the magnetic field downwind of the shock. In mid 2002, Voyager 1 began observing strong energetic beams of termination shock particles, streaming outward along the spiral magnetic field upstream the shock. This led to the suggestion that the termination shock is a blunt structure. Recently we showed that an interstellar magnetic field can produce a north/south asymmetry in the solar wind termination shock, consistent with Voyager 1 observation of the direction of streaming of the particles. These recent surprises indicate that a global understanding of the heliosphere is crucial. In this talk, I will review the current understanding of the edge the solar system, indicate predictions of what Voyager 2 will encounter, and describe the directions that research should take to understand the global structure of the heliosphere.
- Publication:
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AAS/Solar Physics Division Meeting #37
- Pub Date:
- June 2006
- Bibcode:
- 2006SPD....37.2301O