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Enhancements of energetic particles near the heliospheric termination shock

Nature volume 426, pages 48–51 (2003)Cite this article

Abstract

The spacecraft Voyager 1 is at a distance greater than 85 au from the Sun, in the vicinity of the termination shock that marks the abrupt slowing of the supersonic solar wind and the beginning of the extended and unexplored distant heliosphere1,2. This shock is expected to accelerate ‘anomalous cosmic rays’3, as well as to re-accelerate Galactic cosmic rays5 and low-energy particles from the inner Solar System4. Here we report a significant increase in the numbers of energetic ions and electrons that persisted for seven months beginning in mid-2002. This increase differs from any previously observed in that there was a simultaneous increase in Galactic cosmic ray ions and electrons, anomalous cosmic rays and low-energy ions. The low-intensity level and spectral energy distribution of the anomalous cosmic rays, however, indicates that Voyager 1 still has not reached the termination shock. Rather, the observed increase is an expected precursor event. We argue that the radial anisotropy of the cosmic rays is expected to be small in the foreshock region, as is observed.

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Figure 1: Time histories (5-day moving averages) of Voyager 1 cosmic ray intensities.
Figure 2: Time histories (5-day moving averages) of Voyager 1 (V1) and Voyager 2 (V2) cosmic-ray intensities.
Figure 3: Voyager 1 and Voyager 2 energy spectra (2002/209–2002/364).

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References

  1. Parker, E. N. Interplanetary Dynamical Processes 115–128 (Interscience Division, John Wiley and Sons, New York, 1963)

    MATH  Google Scholar 

  2. Holzer, T. E. Interaction between the solar wind and the interstellar medium. Annu. Rev. Astron. Astrophys. 270, 199–234 (1989)

    Article  ADS  Google Scholar 

  3. Pesses, M. E., Jokipii, J. R. & Eichler, D. Cosmic ray drift, shock wave acceleration and the anomalous component of cosmic rays. Astrophys. J. 246, L85–L88 (1981)

    Article  ADS  CAS  Google Scholar 

  4. Mewaldt, R. Solar and interplanetary particles reaccelerated at the solar wind termination shock. Proc. 24th ICRC (Rome) 3, 804–807 (1995)

    Google Scholar 

  5. Jokipii, J. R., Kota, J. & Merenyi, E. The gradient of galactic cosmic rays at the solar wind termination shock. Astrophys. J. 405, 782–786 (1993)

    Article  ADS  Google Scholar 

  6. Stone, E. C. et al. Cosmic ray investigations for the Voyager missions: Energetic particle studies in the outer heliosphere—and beyond. Space Sci. Rev. 21, 355–376 (1977)

    ADS  Google Scholar 

  7. Cummings, A. C., Stone, E. C. & Steenberg, C. D. Composition of anomalous cosmic rays and other interplanetary ions. Astrophys. J. 578, 194–210 (2002)

    Article  ADS  CAS  Google Scholar 

  8. Cummings, A. C. et al. Voyager 1 observations of the anisotropies of enhanced MeV ion fluxes at 85au. Proc. 28th ICRC (Tsukuba) 7, 3777–3780 (2003)

    Google Scholar 

  9. Krimigis, S. M. et al. Voyager 1 left the solar wind at a distance of ∼85au from the Sun. Nature 426 45–48 (2003)

    Article  ADS  CAS  Google Scholar 

  10. Jokipii, J. R., Giacalone, J. & Kota, J. Anomalous cosmic ray and plasma signatures of a termination shock crossing. Geophys. Res. Lett. (submitted)

  11. Chalov, S. V. & Fahr, H. J. Pick-up ion acceleration at the termination shock and the post-shock pick-up ion energy distribution. Astron. Astrophys. 360, 381–390 (2000)

    ADS  Google Scholar 

  12. Jokipii, J. R. & Giacalone, J. Anomalous cosmic rays at a termination shock crossing. Proc. 28th ICRC (Tsukuba) 7, 3753–3756 (2003)

    Google Scholar 

  13. Burlaga, L. F. et al. Search for the heliosheath with Voyager 1 magnetic field measurements. Geophys. Res. Lett. (in the press)

  14. Van Allen, J. A. & Fillius, R. W. Propagation of large Forbush decreases in cosmic ray intensity past the Earth, Pioneer 11 at 34au and Pioneer 10 at 53au. Geophys. Res. Lett. 19, 1423–1426 (1992)

    Article  ADS  CAS  Google Scholar 

  15. Webber, W. R. & Lockwood, J. A. Giant transient decreases of cosmic rays in the outer heliosphere in September 1991. J. Geophys. Res. 98, 7821–7826 (1991)

    Article  ADS  Google Scholar 

  16. Gurnett, D. A., Kurth, W. S., Allendorf, S. C. & Poynter, R. L. Radio emission from the heliopause triggered by an interplanetary shock. Science 262, 199–203 (1993)

    Article  ADS  CAS  Google Scholar 

  17. Lukasiak, A. et al. The Voyager electron telescope—A status report. Proc. 26th ICRC (Salt Lake City) 3, 65–68 (1999)

    Google Scholar 

  18. Gloeckler, G. et al. Acceleration of interstellar pickup ions in the disturbed solar wind observed on Ulysses. J. Geophys. Res. 99, 17637–17643 (1994)

    Article  ADS  Google Scholar 

  19. Schwadron, N. A. & McComas, D. J. Heliospheric “Falts”: Favored Acceleration Locations at the Termination Shock. Geophys. Res. Lett. 30, doi:10.1029/2002GLO16499 (2003)

  20. Christon, S. P. & Stone, E. C. Latitude variation of recurrent MeV energy proton flux enhancements in the radial range 11–20au and possible correlation with solar coronal hole dynamics. Geophys. Res. Lett. 12, 109–112 (1985)

    Article  ADS  CAS  Google Scholar 

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Acknowledgements

We thank J. D. Richardson and colleagues for making the Voyager 2 solar wind data available at 〈http://web.mit.edu/afs/athena/org/s/space/www/voyager.html〉. We also thank J. R. Jokipii, F. C. Jones, H. Moraal, V. Ptuskin and R. Caballero-Lopez for discussions on shock acceleration processes and particle flow in the vicinity of the acceleration region.

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Authors and Affiliations

  1. Institute for Physical Science and Technology, University of Maryland, College Park, Maryland, 20742, USA

    Frank B. McDonald

  2. NASA/Goddard Space Flight Center, Maryland, 20771, Greenbelt, USA

    Bryant Heikkila & Nand Lal

  3. California Institute of Technology, California, 91125, Pasadena, USA

    Edward C. Stone & Alan C. Cummings

  4. Department of Physics and Astronomy, New Mexico State University, 88003, Las Cruces, New Mexico, USA

    William R. Webber

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  1. Frank B. McDonald
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Correspondence to Frank B. McDonald.

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McDonald, F., Stone, E., Cummings, A. et al. Enhancements of energetic particles near the heliospheric termination shock. Nature 426, 48–51 (2003). https://doi.org/10.1038/nature02066

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