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Some Peculiar Features In Saturn’s Rings

Some Peculiar Features In Saturn’s Rings. Quentin Donnellan. “In the universe there are spheres and there are discs; given the correct mechanisms one can become the other” Carolyn Porco. Basics…. 99.9% pure water ice 3x10 19 kg 5-30 m thick. > 5 cm. Cassini radio image. large. < 5 cm.

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Some Peculiar Features In Saturn’s Rings

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  1. Some Peculiar Features In Saturn’s Rings Quentin Donnellan

  2. “In the universe there are spheres and there are discs; given the correct mechanisms one can become the other” Carolyn Porco

  3. Basics… 99.9% pure water ice 3x1019 kg 5-30 m thick > 5 cm Cassini radio image large < 5 cm

  4. Particle size Roche limit Particles over a certain size will be torn apart by tidal forces Accretion discs inside the Roche limit should not coalesce beyond a certain size

  5. Dominant features *Titan

  6. Dominant features *Mimas

  7. Dominant Features Daphnis Pan

  8. Moons carve out gaps/features Rings are Keplerian…

  9. Some disturbances are quite elegant

  10. Teamwork F-Ring Prometheus Pandora

  11. Some are not big enough… Moonlets embedded in the rings create keplerian wakes

  12. Propellers

  13. Upon further inspection, it ain’t that simple…

  14. Density Waves In the 1960’s astronomers theorized the origins of spiral arms in galaxies as artifacts of “density waves”

  15. Density Waves “Traffic Jams” of material increase the local density of the galactic disc and increase the local rate of star formation

  16. Well, the rings around Saturn are essentially just a “disc”…

  17. Density Waves at Saturn Analogous to spiral arms of galaxies, just much more tightly wound, caused by resonance excitation by moons

  18. Also bending… bending wave (Vertical undulations) Density wave 2004, A ring

  19. This is advanced dynamics

  20. So we can explain all of the peculiarities in the rings by the tugging of moons… … right?

  21. Viscosity B ring: very dense We would expect such a high viscosity to dampen any waves excited into this ring

  22. Viscosity But the viscosity of the ring is such that the random motions of the particles in the ring actually amplify waves

  23. The rings, much like guitar strings, have natural modes which can become self-excited and amplified due to “viscous overstability” http://www.youtube.com/watch?v=tA2eqTZijwI

  24. The equinox reveals more clues

  25. I know you’re there Janus

  26. Back to Daphnis

  27. Vertical Structures 1-3 km in height

  28. Back to the B-Ring

  29. Back to the propellers

  30. Complicated system… So the rings are very complicated Waves induced by moons Paths cut out by moons Material dragged up and down by moons Waves induced by the rings themselves

  31. Extensions Can we treat all disc structures similarly?

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