Dec. 31, 2009 Saturn emits "auroral hiss," a whistler-mode electromagnetic emission observed in the magnetosphere at high latitudes. This emission is similar to auroral hiss emitted by Earth. However, unlike Earth's auroral hiss, Gurnett et al. find that Saturn rotates in a beam-like matter around the planet.
Using data taken by the Cassini spacecraft, the authors observe that the auroral hiss emitted by Saturn has a different rotation rate in the northern and southern hemispheres; the period is about 10.6 hours in the northern hemisphere and about 10.8 hours in the southern hemisphere. They note that the rotation periods match the modulation periods of another type of radio emission, Saturn kilometric radiation, which was also recently found to rotate at different rates in the two hemispheres.
This new observation confirms a fundamental north-south asymmetry in the rotation rates of high-latitude plasma phenomena in the two hemispheres.
The authors suggest that the results also have implications for understanding how the planet's rotation is transferred to the magnetosphere plasma.
The research is published in Geophysical Research Letters. Authors include D. A. Gurnett, A. M. Persoon, J. B. Groene, A. J. Kopf, G. B. Hospodarsky, W. S. Kurth: Department of Physics and Astronomy, University of Iowa, Iowa City, Iowa, USA.
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- Gurnett et al. A north-south difference in the rotation rate of auroral hiss at Saturn: Comparison to Saturn's kilometric radio emission. Geophysical Research Letters, 2009; 36 (21): L21108 DOI: 10.1029/2009GL040774
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