Search for the Exit: Voyager 1 at Heliosphere’s Border with the Galaxy

Science  27 Jun 2013:
DOI: 10.1126/science.1235721

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We report measurements of energetic (>40 keV) charged particles on Voyager 1 (V1) from the interface region between the heliosheath (HS), dominated by heated solar plasma, and the local interstellar medium (LISM) expected to contain cold nonsolar plasma and the galactic magnetic field. Particles of solar origin at V1, located at 18.5 billion km (123 AU) from the Sun, decreased by a factor >103 on 25 August 2012, while those of galactic origin (cosmic rays) increased by 9.3% at the same time. Intensity changes appeared first for particles moving in the azimuthal direction and were followed by those moving in the radial and antiradial directions with respect to the solar radius vector. This unexpected heliospheric "depletion region" may form part of the interface between solar plasma and the galaxy.

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