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Cool heliosheath plasma and deceleration of the upstream solar wind at the termination shock


The solar wind blows outward from the Sun and forms a bubble of solar material in the interstellar medium. The termination shock occurs where the solar wind changes from being supersonic (with respect to the surrounding interstellar medium) to being subsonic. The shock was crossed by Voyager 1 at a heliocentric radius of 94 au (1 au is the Earth–Sun distance) in December 2004 (refs 1–3). The Voyager 2 plasma experiment observed a decrease in solar wind speed commencing on about 9 June 2007, which culminated in several crossings of the termination shock between 30 August and 1 September 2007 (refs 4–7). Since then, Voyager 2 has remained in the heliosheath, the region of shocked solar wind. Here we report observations of plasma at and near the termination shock and in the heliosheath. The heliosphere is asymmetric, pushed inward in the Voyager 2 direction relative to the Voyager 1 direction. The termination shock is a weak, quasi-perpendicular shock that heats the thermal plasma very little. An unexpected finding is that the flow is still supersonic with respect to the thermal ions downstream of the termination shock. Most of the solar wind energy is transferred to the pickup ions or other energetic particles both upstream of and at the termination shock.

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Figure 1: An overview of data near the termination shock.
Figure 2: High-resolution (192 s) solar wind speed ( V R ) near the termination shock crossings.
Figure 3: High-resolution data near the termination shock crossings (shaded regions).
Figure 4: Most of the solar wind flow energy does not go into the solar wind plasma.
Figure 5: The termination shock is very different from other shocks observed in the heliosphere.


  1. Decker, R. B. et al. Voyager 1 in the foreshock, termination shock, and heliosheath. Science 309, 2020–2024 (2005)

    Article  CAS  ADS  Google Scholar 

  2. Burlaga, L. F. et al. Crossing the termination shock into the heliosheath: magnetic fields. Science 309, 2027–2029 (2005)

    Article  CAS  ADS  Google Scholar 

  3. Stone, E. C. et al. Voyager 1 explores the termination shock region and the heliosheath beyond. Science 309, 2017–2020 (2005)

    Article  CAS  ADS  Google Scholar 

  4. Burlaga, L. F. et al. Magnetic fields at the solar wind termination shock. Nature 10.1038/nature07029 (this issue)

  5. Decker, R. B. et al. Mediation of the solar wind termination shock by non-thermal ions. Nature 10.1038/nature07030 (this issue)

  6. Gurnett, D. A. & Kurth, W. S. Intense plasma waves at and near the solar wind termination shock. Nature 10.1038/nature07023 (this issue)

  7. Stone, E. C. et al. An asymmetric solar wind termination shock. Nature 10.1038/nature07022 (this issue)

  8. Bridge, H. S. et al. The plasma experiment on the 1977 Voyager mission. Space Sci. Rev. 21, 259–287 (1977)

    Article  ADS  Google Scholar 

  9. Opher, M., Stone, E. C. & Liewer, P. C. The effects of a local interstellar magnetic field on Voyager 1 and 2 observations. Astrophys. J. 640, L71–L74 (2006)

    Article  ADS  Google Scholar 

  10. Pogorelov, N. V., Zank, G. P. & Ogino, T. Three-dimensional features of the outer heliosphere due to coupling between the interstellar and interplanetary magnetic fields. II. The presence of neutral hydrogen atoms. Astrophys. J. 644, 1299–1316 (2006)

    Article  CAS  ADS  Google Scholar 

  11. Lallement, R. et al. Deflection of the interstellar neutral hydrogen flow across the heliospheric interface. Science 307, 1447–1449 (2005)

    Article  CAS  ADS  Google Scholar 

  12. Izmodenov, V., Malama, Y. G. & Ruderman, M. Solar cycle influence on the interaction of the solar wind with Local Interstellar Cloud. Astron. Astrophys. 429, 1069–1080 (2005)

    Article  CAS  ADS  Google Scholar 

  13. Gurnett, D. A. & Kurth, W. S. Electron plasma oscillations upstream of the solar wind termination shock. Science 309, 2025–2027 (2005)

    Article  CAS  ADS  Google Scholar 

  14. Opher, M., Stone, E. C. & Gombosi, T. I. The orientation of the local interstellar magnetic field. Science 316, 875–878 (2007)

    Article  CAS  ADS  Google Scholar 

  15. Jokipii, J. R., Giacalone, J. & Kota, J. Transverse streaming anisotropies of charged particles accelerated at the solar wind termination shock. Astrophys. J. 611, L141–L144 (2004)

    Article  ADS  Google Scholar 

  16. Gloeckler, G., Fisk, L. A. & Lanzerotti, L. J. Acceleration of solar wind and pickup ions by shocks, in Connecting Sun and Heliosphere (Proc. Solar Wind 11/SOHO 16 Conf.) (eds Fleck, B., Zurbuchen, T. H. & Lacoste, H.) 107–112 (ESA, Noordwijk, 2005)

    Google Scholar 

  17. Zank, G., Pauls, H., Cairns, I. & Webb, G. Interstellar pickup ions and quasi-perpendicular shocks: Implications for the termination shock and interplanetary shocks. J. Geophys. Res. 101, 457–477 (1996)

    Article  ADS  Google Scholar 

  18. Lipatov, A. S. & Zank, G. P. Pickup ion acceleration at low-β p perpendicular shocks. Phys. Rev. Lett. 82, 3609–3612 (1999)

    Article  CAS  ADS  Google Scholar 

  19. Giacalone, J. & Burgess, D. Hybrid simulations of the interaction of a current sheet with the termination shock. Eos 88 (Fall meeting), abstr. SH12B-05 (2007)

  20. Pogorelov, N. V., Stone, E. C., Florinski, V. & Zank, G. P. Termination shock asymmetries as seen by the Voyager spacecraft: The role of the interstellar magnetic field and neutral hydrogen. Astrophys. J. 668, 611–624 (2007)

    Article  CAS  ADS  Google Scholar 

  21. Wang, C., Richardson, J. D. & Paularena, K. I. Predicted Voyager observations of the Bastille Day 2000 coronal mass ejection. J. Geophys. Res. 106, 13007–13013 (2001)

    Article  ADS  Google Scholar 

  22. Berdichevsky, D. B., Szabo, A., Lepping, R., Viñas, A. & Mariani, F. Interplanetary fast shocks and associated drivers observed through the 23rd solar minimum by Wind over its first 2.5 years. J. Geophys. Res. 105, 27289–27314 (2000)

    Article  ADS  Google Scholar 

  23. Vinas, A. F. & Scudder, J. D. Fast and optimal solution to the ‘Rankine-Hugoniot problem’. J. Geophys. Res. 91, 39–58 (1986)

    Article  ADS  Google Scholar 

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The work at MIT is supported by NASA. C.W. is grateful for support from NNSFC. Magnetic field data are shown courtesy of the Voyager magnetometer team (principle investigator N. Ness). We thank G. Gordon, Jr and L. Finck for development of and assistance with the plasma analysis.

Author Contributions J.D.R. analysed the plasma data and wrote the paper. J.C.K. performed the calculations for and write-up of the shock parameters. C.W. calculated the termination shock motion. J.W.B. and A.J.L. assisted with design of the instrument and manuscript preparation.

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Correspondence to John D. Richardson.

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Data from the Voyager 2 plasma experiment are available at

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Richardson, J., Kasper, J., Wang, C. et al. Cool heliosheath plasma and deceleration of the upstream solar wind at the termination shock. Nature 454, 63–66 (2008).

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