Turbulent viscosity and lifetime of Saturn's rings

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5 Scopus citations


The viscosity (the angular momentum flux) in the disk of mutually gravitating particles of Saturn's rings is investigated. The hydrodynamic theory of the gravitational Jeans-type instability of small gravity perturbations (e.g., those produced by spontaneous disturbances) of the disk is developed. It is suggested that in such a system the hydrodynamic turbulence may arise as a result of the instability. The turbulence is related to stochastic motions of "fluid" elements. The objective of this paper is to show that in the Jeans-unstable Saturnian ring disk the turbulent viscosity may exceed the ordinary microscopic viscosity substantially. The main result of local N-body simulations of planetary rings by Daisaka et al. (2001. Viscosity in a dense planetary ring with self-gravitating particles. Icarus 154, 296-312) is explained: in the presence of the gravitationally unstable density waves, the effective turbulent viscosity νeff is given as νeff = CG2 Σ2 / Ω3, where G, Σ, and Ω are the gravitational constant, the surface mass density of a ring, and the angular velocity, respectively, and the nondimensional correction factor C ≈ 10. We argue that both Saturn's main rings and their irregular of the order of 100 m or even less fine-scale structure (being recurrently created and destroyed on the time scale of an order of Keplerian period ∼ 10 h) are not likely much younger than the solar system.

Original languageEnglish
Pages (from-to)794-807
Number of pages14
JournalPlanetary and Space Science
Issue number8
StatePublished - 1 Aug 2006


  • Planets
  • Rings-planets and satellites
  • Saturn-instabilities and waves

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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