Skip to main content

Thank you for visiting 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.

An Earth-like correspondence between Saturn's auroral features and radio emission


Saturn is a source of intense kilometre-wavelength radio emissions that are believed to be associated with its polar aurorae1,2, and which provide an important remote diagnostic of its magnetospheric activity. Previous observations implied that the radio emission originated in the polar regions, and indicated a strong correlation with solar wind dynamic pressure1,3,4,5,6,7. The radio source also appeared to be fixed near local noon and at the latitude of the ultraviolet aurora1,2. There have, however, been no observations relating the radio emissions to detailed auroral structures. Here we report measurements of the radio emissions, which, along with high-resolution images of Saturn's ultraviolet auroral emissions8, suggest that although there are differences in the global morphology of the aurorae, Saturn's radio emissions exhibit an Earth-like correspondence between bright auroral features and the radio emissions. This demonstrates the universality of the mechanism that results in emissions near the electron cyclotron frequency narrowly beamed at large angles to the magnetic field9,10.

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

Relevant articles

Open Access articles citing this article.

Access options

Buy article

Get time limited or full article access on ReadCube.


All prices are NET prices.

Figure 1: Correlations between auroral input power and emitted SKR power.
Figure 2: Detailed SKR observations from 8 January and the associated ultraviolet images.
Figure 3: Beaming angles required to illuminate Cassini from radio sources associated with bright spots identified in Fig. 2.


  1. Kaiser, M. L. et al. in Saturn (eds Gehrels, T. & Matthews, M. S.) 378–415 (Univ. Arizona Press, Tucson, 1984)

    Google Scholar 

  2. Galopeau, P. H. M., Zarka, P. & Le Quéau, D. Source location of Saturn's kilometric radiation: The Kelvin-Helmholtz instability hypothesis. J. Geophys. Res. 100, 26397–26410 (1995)

    ADS  Article  Google Scholar 

  3. Warwick, J. W. et al. Planetary radio astronomy observations from Voyager 1 near Saturn. Science 212, 239–243 (1981)

    ADS  CAS  Article  Google Scholar 

  4. Galopeau, P. H. M. & Lecacheux, A. Variations in Saturn's radio rotation period measured at kilometer wavelengths. J. Geophys. Res. 105, 13089–13101 (2000)

    ADS  Article  Google Scholar 

  5. Zarka, P. in Planetary Radio Emissions II (eds Rucker, H. O., Bauer, S. J. & Pedersen, B. M.) 327–342 (Austrian Acad. Sci. Press, Vienna, 1988)

    Google Scholar 

  6. Zarka, P. Auroral radio emissions at the outer planets: Observations and theories. J. Geophys. Res. 103, 20159–20194 (1998)

    ADS  Article  Google Scholar 

  7. Desch, M. D. Evidence for solar wind control of Saturn radio emission. J. Geophys. Res. 87, 4549–4554 (1982)

    ADS  Article  Google Scholar 

  8. Clarke, J. T. et al. Morphological differences of Saturn's ultraviolet aurorae and those of Earth and Jupiter. Nature doi:10.1038/nature03331 (this issue)

  9. Wu, C. S. & Lee, L. C. A theory of terrestrial kilometric radiation. Astrophys. J. 230, 621–626 (1979)

    ADS  CAS  Article  Google Scholar 

  10. Galopeau, P., Zarka, P. & Le Quéau, D. Theoretical model of Saturn's kilometric radiation spectrum. J. Geophys. Res. 94, 8739–8755 (1989)

    ADS  Article  Google Scholar 

  11. Connerney, J. E. P., Ness, N. F. & Acuña, M. H. Zonal harmonic model of Saturn's magnetic field from Voyager 1 and 2 observations. Nature 298, 44–46 (1982)

    ADS  Article  Google Scholar 

  12. Galopeau, P., Ortega-Molina, A. & Zarka, P. Evidence of Saturn's magnetic field anomaly from SKR high-frequency limit. J. Geophys. Res. 96, 14129–14140 (1991)

    ADS  Article  Google Scholar 

  13. Galopeau, P. & Zarka, P. Reply to the comment by J. E. P. Connerney and M. D. Desch on “Evidence of Saturn's magnetic field anomaly from SKR high-frequency limit”. J. Geophys. Res. 97, 12291–12297 (1992)

    ADS  Article  Google Scholar 

  14. Gurnett, D. A. et al. The Cassini radio and plasma wave science investigation. Space Sci. Rev. (in the press)

  15. Gurnett, D. A. The Earth as a radio source: Terrestrial kilometric radiation. J. Geophys. Res. 79, 4227–4238 (1974)

    ADS  Article  Google Scholar 

  16. Crary, F. J. et al. Solar wind dynamic pressure and electric field as the main factors controlling Saturn's aurorae. Nature doi:10.1038/nature03333 (this issue)

  17. Huff, R. L., Calvert, W., Craven, J. D., Frank, L. A. & Gurnett, D. A. Mapping of auroral kilometric radiation sources to the aurora. J. Geophys. Res. 93, 11445–11454 (1988)

    ADS  Article  Google Scholar 

  18. de Feraudy, H., Bahnsen, A. & Jespersen, M. in Planetary Radio Emissions II (eds Rucker, H. O., Bauer, S. J. & Pedersen, B. M.) 41–60 (Austrian Acad. Sci. Press, Vienna, 1988)

    Google Scholar 

  19. Stone, R. G. et al. The unified radio and plasma wave investigation. Astron. Astrophys. Suppl. Ser. 92, 291–316 (1992)

    ADS  Google Scholar 

  20. Wenzel, K. P., Marsden, R. G., Page, D. E. & Smith, E. J. The Ulysses mission. Astron. Astrophys. Suppl. Ser. 92, 207–219 (1992)

    ADS  CAS  Google Scholar 

  21. Imhof, W. L. et al. The dependence of AKR production on the intensity and energy spectra of auroral bremsstrahlung. J. Geophys. Res. 108, doi:10.1029/2002JA009274 (2003)

  22. Knight, S. Parallel electric fields. Planet. Space Sci. 21, 741–750 (1973)

    ADS  Article  Google Scholar 

  23. Cowley, S. W. H. & Bunce, E. J. Origin of the main auroral oval in Jupiter's coupled magnetosphere-ionosphere system. Planet. Space Sci. 49, 1067–1088 (2001)

    ADS  Article  Google Scholar 

Download references


This research was supported by NASA through contracts with the Jet Propulsion Laboratory. J.-C.G. and D.G. are supported by the Belgian Fund for Scientific Research (FNRS) and partly funded by the PRODEX programme of the European Space Agency. This work is based on observations with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by AURA, Inc., for NASA.

Author information

Authors and Affiliations


Corresponding author

Correspondence to W. S. Kurth.

Ethics declarations

Competing interests

The authors declare that they have no competing financial interests.

Rights and permissions

Reprints and Permissions

About this article

Cite this article

Kurth, W., Gurnett, D., Clarke, J. et al. An Earth-like correspondence between Saturn's auroral features and radio emission. Nature 433, 722–725 (2005).

Download citation

  • Received:

  • Accepted:

  • Issue Date:

  • DOI:

Further reading


By submitting a comment you agree to abide by our Terms and Community Guidelines. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate.


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