Our heliosphere: The new view from Voyager

Abstract

Launched in 1977 on a journey to the giant outer planets and beyond, Voyager 1 and 2 have explored the spatial and dynamical properties of the heliosphere that modulates the inward flow of galactic cosmic rays and is the source of anomalous cosmic rays. The two spacecraft are in the heliosheath beyond the termination shock where the supersonic solar wind has slowed as it approaches the boundary of the heliosphere. The shock crossing was 10 AU closer at Voyager 2 in the south than at Voyager 1 in the north, indicating a local interstellar magnetic field pressing inward more strongly on the southern hemisphere. The expected source of anomalous cosmic rays was not observed at the shock, and their intensity has increased deeper in the heliosheath, indicating the source is elsewhere on the shock or in the heliosheath. Voyager 1, now at 121 AU at 35 degrees north, has been in a quasi-stagnation region since 2010 where there is no outward motion of the wind, the magnetic field is enhanced, and the galactic cosmic ray intensity is increasing. In contrast, the heliosheath flow at Voyager 2 at 99 AU and 30 degrees south is faster and increasingly deflected in a non-radial direction as it turns to flow tailward. These observations will be placed in the context of current models of the interaction of the solar and interstellar winds.

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