An asymmetric solar wind termination shock

Voyager 2 crossed the solar wind termination shock at 83.7 au in the southern hemisphere, ∼10 au closer to the Sun than found by Voyager 1 in the north. This asymmetry could indicate an asymmetric pressure from an interstellar magnetic field, from transient-induced shock motion, or from the solar wi...

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Bibliographic Details
Published in:Nature 2008-07, Vol.454 (7200), p.71-74
Main Authors: Stone, Edward C, Cummings, Alan C, McDonald, Frank B, Heikkila, Bryant C, Lal, Nand, Webber, William R
Format: Article
Language:English
Subjects:
Astronomy
Cosmic rays
Earth, ocean, space
Electrons
Exact sciences and technology
Heliosphere
Helium
Humanities and Social Sciences
Interplanetary space
Ions
letter
Magnetic fields
multidisciplinary
Natural history
Observations
Science
Science (multidisciplinary)
Shock waves
Solar energy
Solar system
Solar wind
Solar wind plasma
Space probes
Wind power
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Summary:Voyager 2 crossed the solar wind termination shock at 83.7 au in the southern hemisphere, ∼10 au closer to the Sun than found by Voyager 1 in the north. This asymmetry could indicate an asymmetric pressure from an interstellar magnetic field, from transient-induced shock motion, or from the solar wind dynamic pressure. Here we report that the intensity of 4-5 MeV protons accelerated by the shock near Voyager 2 was three times that observed concurrently by Voyager 1, indicating differences in the shock at the two locations. (Companion papers report on the plasma, magnetic field, plasma-wave and lower energy particle observations at the shock.) Voyager 2 did not find the source of anomalous cosmic rays at the shock, suggesting that the source is elsewhere on the shock or in the heliosheath. The small intensity gradient of Galactic cosmic ray helium indicates that either the gradient is further out in the heliosheath or the local interstellar Galactic cosmic ray intensity is lower than expected.
ISSN:0028-0836
1476-4687
1476-4679
DOI:10.1038/nature07022