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Cosmic ray measurements from Voyager 2 as it crossed into interstellar space

Stone, Edward C. and Cummings, Alan C. and Heikkila, Bryant C. and Lal, Nand (2019) Cosmic ray measurements from Voyager 2 as it crossed into interstellar space. Nature Astronomy, 3 (11). pp. 1013-1018. ISSN 2397-3366. doi:10.1038/s41550-019-0928-3.

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The interaction of the interstellar and solar winds is complex, as revealed by differences in intensities and anisotropies of low-energy ions (>0.5 MeV per nucleon) originating inside the heliosphere and those of higher-energy Galactic cosmic rays (>70 MeV per nucleon) originating outside, in the Milky Way. On 5 November 2018, Voyager 2 observed a sharp decrease in the intensity of low-energy ions and a simultaneous increase in the intensity of cosmic rays, indicating that Voyager 2 had crossed the heliopause at 119 au and entered interstellar space about six years after Voyager 1. Unlike Voyager 1, which found that two interstellar flux tubes had invaded the heliosheath and served as precursors to the heliopause, Voyager 2 found no similar precursors. However, just beyond the heliopause Voyager 2 discovered a boundary layer, in which low-energy particles streamed outward along the magnetic field and cosmic ray intensities were only 90% of those further out.

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Stone, Edward C.0000-0002-2010-5462
Cummings, Alan C.0000-0002-3840-7696
Additional Information:© 2019 Springer Nature Limited. Received 21 July 2019; Accepted 27 September 2019; Published 04 November 2019. Data availability: Most of the CRS data can be obtained by clicking on the DATA link at and following other links to obtain rate and flux data. All data that were used in the figures can be provided by the corresponding author on request. We thank L. Burlaga for providing magnetic field data before publication. A.C.C. acknowledges support from the International Space Sciences Institute in Bern, Switzerland, to participate in the international team The Physics of the Very Local Interstellar Medium in the autumn of 2018. This work was supported by NASA under grant NNN12AA01C. Author Contributions: All authors contributed to the production of this manuscript. A.C.C. and E.C.S. wrote the text. A.C.C., B.C.H. and N.L. performed the data analysis and A.C.C. and B.C.H. prepared the figures. All authors participated in reviewing and commenting on the paper and on the editor’s and referees’ comments. The authors declare no competing interests.
Group:Space Radiation Laboratory
Funding AgencyGrant Number
Subject Keywords:Astronomy and planetary science; Space physics
Issue or Number:11
Record Number:CaltechAUTHORS:20190926-164717298
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Official Citation:Stone, E.C., Cummings, A.C., Heikkila, B.C. et al. Cosmic ray measurements from Voyager 2 as it crossed into interstellar space. Nat Astron 3, 1013–1018 (2019) doi:10.1038/s41550-019-0928-3
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:98892
Deposited By: George Porter
Deposited On:04 Nov 2019 18:54
Last Modified:16 Nov 2021 17:42

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