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

Abstract

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.

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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.

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References

  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)

    Article  ADS  Google Scholar 

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

    Article  ADS  CAS  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)

    Article  ADS  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)

    Article  ADS  Google Scholar 

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

    Article  ADS  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)

    Article  ADS  CAS  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)

    Article  ADS  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)

    Article  ADS  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)

    Article  ADS  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)

    Article  ADS  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)

    Article  ADS  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)

    Article  ADS  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)

    Article  ADS  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)

    Article  ADS  Google Scholar 

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Acknowledgements

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.

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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). https://doi.org/10.1038/nature03334

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