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Published November 1, 2014 | public
Journal Article

Saturn ring seismology: Evidence for stable stratification in the deep interior of Saturn

Fuller, Jim ORCID icon


Seismology allows for direct observational constraints on the interior structures of stars and planets. Recent observations of Saturn's ring system have revealed the presence of density waves within the rings excited by oscillation modes within Saturn, allowing for precise measurements of a limited set of the planet's mode frequencies. We construct interior structure models of Saturn, compute the corresponding mode frequencies, and compare them with the observed mode frequencies. The fundamental mode frequencies of our models match the observed frequencies (of the largest amplitude waves) to an accuracy of ∼1%, confirming that these waves are indeed excited by Saturn's f-modes. The presence of the lower amplitude waves (finely split in frequency from the f-modes) can only be reproduced in models containing gravity modes that propagate in a stably stratified region of the planet. The stable stratification must exist deep within the planet near the large density gradients between the core and envelope. Our models cannot easily reproduce the observed fine splitting of the m=-3 modes, suggesting that additional effects (e.g., significant latitudinal differential rotation) may be important.

Additional Information

© 2014 Elsevier Inc. All rights reserved. Received 12 June 2014, Revised 26 July 2014, Accepted 7 August 2014, Available online 15 August 2014. I thank Matt Hedman, Phil Nicholson, Yanqin Wu, Dave Stevenson, Mark Marley, and Gordon Ogilvie for helpful discussions. I acknowledge partial support from NSF under Grant No. AST-1205732 and through a Lee DuBridge Fellowship at Caltech. This research was supported in part by the National Science Foundation under Grant No. NSF PHY11-25915.

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