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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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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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