Skip to main content

Thank you for visiting nature.com. You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

  • Article
  • Published:

Voyager 2 plasma observations of the heliopause and interstellar medium

Abstract

The solar wind blows outwards from the Sun and forms a bubble of solar material in the interstellar medium. The heliopause (HP) is the boundary that divides the hot tenuous solar wind plasma in the heliosheath from the colder, denser very local interstellar medium (VLISM). The Voyager 2 plasma experiment observed the HP crossing from the solar wind into the VLISM on 5 November 2018 at 119 au. Here we present the first measurements of plasma at and near the HP and in the VLISM. A plasma boundary region with a width of 1.5 au is observed before the HP. The plasma in the boundary region slows, heats up and is twice as dense as typical heliosheath plasma. A much thinner boundary layer begins about 0.06 au inside the HP where the radial speed decreases and the density and magnetic field increase. The HP transition occurs in less than one day. The VLISM is variable near the HP and hotter than expected. Voyager 2 observations show that the temperature is 30,000–50,000 K, whereas models and observations predicted a VLISM temperature of 15,000–30,000 K.

This is a preview of subscription content, access via your institution

Access options

Rent or buy this article

Prices vary by article type

from$1.95

to$39.95

Prices may be subject to local taxes which are calculated during checkout

Fig. 1: Current observed by the V2 PLS experiment in the three Faraday cups that look sunwards.
Fig. 2: Daily averages of solar wind speed, density, temperature, magnetic field magnitude and GCR count rates.
Fig. 3: Plasma velocity components observed by V1 and V2 in the heliosheath in the RTN coordinate system.
Fig. 4: The HP boundary layer extends from day 302 to the HP.
Fig. 5: Currents observed in the PLS D cup, which looks closest to the VLISM flow.
Fig. 6: Contours of currents in the 10–30 eV channel of the D cup.
Fig. 7: Observations of plasma currents in selected high-energy resolution M mode channels during the V2 rolls in 2019.

Similar content being viewed by others

Data availability

Data from the Voyager Plasma experiment are available at http://web.mit.edu/space/www/voyager.html

References

  1. Burlaga, L. F. et al. Magnetic field observations as Voyager 1 entered the heliosheath depletion region. Science 341, 147–150 (2013).

    Article  ADS  Google Scholar 

  2. Gurnett, D. A., Kurth, W. S., Burlaga, L. F. & Ness, N. F. In situ observations of interstellar plasma with Voyager 1. Science 341, 1489–1492 (2013).

    Article  ADS  Google Scholar 

  3. Krimigis, S. M. et al. Search for the exit: Voyager 1 at heliosphere’s border with the galaxy. Science 341, 144–147 (2013).

    Article  ADS  Google Scholar 

  4. Stone, E. C. et al. Voyager 1 observes low-energy galactic cosmic rays in a region depleted of heliospheric ions. Science 341, 150–153 (2013).

    Article  ADS  Google Scholar 

  5. Stone, E. C., Cummings, A. C., Heikkila, B. C. & Lal, N. Cosmic ray measurements from Voyager 2 as it crossed into interstellar space. Nat. Astron. https://doi.org/10.1038/s41550-019-0928-3 (2019).

  6. Krimigis, S. M. et al. Energetic charged particle measurements from Voyager 2 at the heliopause and beyond. Nat. Astron. https://doi.org/10.1038/s41550-019-0927-4 (2019).

  7. Burlaga, L. F. et al. Magnetic field and particle measurements made by Voyager 2 at and near the heliopause. Nat. Astron. https://doi.org/10.1038/s41550-019-0920-y (2019).

  8. Gurnett, D. A. & Kurth, W. S. Plasma densities near and beyond the heliopause from the Voyager 1 and 2 plasma wave instruments. Nat. Astron. https://doi.org/10.1038/s41550-019-0918-5 (2019).

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

    Article  ADS  Google Scholar 

  10. Richardson, J. D. et al. Cool heliosheath plasma and deceleration of the upstream solar wind at the termination shock. Nature 464, 63–65 (2008).

    Article  ADS  Google Scholar 

  11. Krimigis, S. M., Roelof, E. C., Decker, R. B. & Hill, M. E. Zero outward flow velocity for plasma in a heliosheath transition layer. Nature 474, 359–361 (2011).

    Article  ADS  Google Scholar 

  12. Burlaga, L. F., Ness, N. F. & Richardson, J. D. Transition from the unipolar region to the sector zone: Voyager 2, 2013 and 2014. Astrophys J. 841, 47–59 (2017).

    Article  ADS  Google Scholar 

  13. Richardson, J. D. et al. Pressure pulses at Voyager 2: drivers of interstellar transients? Astrophys. J. 834, 190–195 (2017).

    Article  ADS  Google Scholar 

  14. Decker, R. B., Krimigis, S. M., Roelof, R. B. & Hill, M. E. No meridional plasma flow in the heliosheath transition region. Nature 489, 124–127 (2012).

    Article  ADS  Google Scholar 

  15. Stone, E. C. & Cummings, A. C. Cosmic rays in the heliosheath. Proc. Int. Cosmic Ray Conf. Beijing 12, 29–32 (2012).

  16. Gurnett, D. A. et al. Precursors to interstellar shocks of solar origin. Astrophys. J. 809, 121–130 (2015).

    Article  ADS  Google Scholar 

  17. McComas, D. J. et al. Local interstellar medium: Six years of direct sampling by IBEX. Astrophys. J. Suppl. Ser. 220, 22–32 (2015).

    Article  ADS  Google Scholar 

  18. Zank, G. Interaction of the solar wind with the local interstellar medium: a theoretical perspective. Space Sci. Rev. 89, 413–688 (1999).

    Article  ADS  Google Scholar 

  19. Fuselier, S. A. & Cairns, I. H. Reconnection at the heliopause: predictions for Voyager 2. J. Phys.Conf. Ser. 900, 012007 (2017).

    Article  Google Scholar 

  20. Barnett, A. & Olbert, S. Response function of modulated grid Faraday cup plasma instruments. Rev. Sci. Instrum. 57, 2432–2440 (1986).

    Article  ADS  Google Scholar 

  21. Richardson, J. D. & Decker, R. B. Voyager 2 observations of plasmas and flows out to 104 AU. Astrophys. J. 792, 126–130 (2014).

    Article  ADS  Google Scholar 

Download references

Acknowledgements

The work at MIT is supported by NASA. Magnetic field and GCR data are shown courtesy of the Voyager Magnetometer (N. Ness, P.I.) and Cosmic Ray Subsystem (E. Stone, P.I.) teams. We thank G. S. Gordon Jr and L. A. Finck for development of, and assistance with, the plasma analysis.

Author information

Authors and Affiliations

Authors

Contributions

J.D.R. analysed the plasma data and wrote the paper. J.W.B. developed the data analysis routines and participated in the design of the instrument. P.G.-G. assisted with the simulations of the currents. L.F.B. analysed the magnetic field data.

Corresponding author

Correspondence to John D. Richardson.

Ethics declarations

Competing interests

The authors declare no competing interests.

Additional information

Peer review information Nature Astronomy thanks George Livadiotis, Brian Wood and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Rights and permissions

Reprints and permissions

About this article

Check for updates. Verify currency and authenticity via CrossMark

Cite this article

Richardson, J.D., Belcher, J.W., Garcia-Galindo, P. et al. Voyager 2 plasma observations of the heliopause and interstellar medium. Nat Astron 3, 1019–1023 (2019). https://doi.org/10.1038/s41550-019-0929-2

Download citation

  • Received:

  • Accepted:

  • Published:

  • Issue Date:

  • DOI: https://doi.org/10.1038/s41550-019-0929-2

This article is cited by

Search

Quick links

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing