Particle properties and the large-scale structure of planetary rings: Rebound characteristics and viscosity

Research output: Contribution to journalArticle

8 Citations (Scopus)

Abstract

In a swarm of particles on Keplerian orbits, like a planetary ring, systematic flow is circular with velocity decreasing with distance from the planet. Viscosity ordinarily transports momentum from a faster to a slower moving region, i.e., outward. But any individual at apocenter of its orbit moves slower, and at pericenter faster, than the mean flow, suggesting a reversed momentum transport or negative viscosity. Resolution of this seeming paradox illuminates the importance of physical properties of particles. A conventional model has uniform, highly elastic, perfectly slippery, spherical particles, with a particular dependence of elasticity on impact velocity. Even slight deviation from that ideal affects viscosity and leads to inconsistencies with observed ring structure. If particles are less elastic they may clump into large temporary agglomerations. The size of the larger bodies in the rings probably determines random velocities, viscosity, and much about ring structure.

Original languageEnglish (US)
Pages (from-to)527-539
Number of pages13
JournalIcarus
Volume75
Issue number3
DOIs
StatePublished - 1988

Fingerprint

planetary rings
viscosity
ring structures
momentum
orbits
impact velocity
paradoxes
clumps
agglomeration
elasticity
planets
planet
elastic properties
physical property
physical properties
deviation
particle
rings

ASJC Scopus subject areas

  • Space and Planetary Science
  • Astronomy and Astrophysics

Cite this

Particle properties and the large-scale structure of planetary rings : Rebound characteristics and viscosity. / Greenberg, Richard J.

In: Icarus, Vol. 75, No. 3, 1988, p. 527-539.

Research output: Contribution to journalArticle

@article{a3c3951fcf3b497fac7d128df7b03edf,
title = "Particle properties and the large-scale structure of planetary rings: Rebound characteristics and viscosity",
abstract = "In a swarm of particles on Keplerian orbits, like a planetary ring, systematic flow is circular with velocity decreasing with distance from the planet. Viscosity ordinarily transports momentum from a faster to a slower moving region, i.e., outward. But any individual at apocenter of its orbit moves slower, and at pericenter faster, than the mean flow, suggesting a reversed momentum transport or negative viscosity. Resolution of this seeming paradox illuminates the importance of physical properties of particles. A conventional model has uniform, highly elastic, perfectly slippery, spherical particles, with a particular dependence of elasticity on impact velocity. Even slight deviation from that ideal affects viscosity and leads to inconsistencies with observed ring structure. If particles are less elastic they may clump into large temporary agglomerations. The size of the larger bodies in the rings probably determines random velocities, viscosity, and much about ring structure.",
author = "Greenberg, {Richard J.}",
year = "1988",
doi = "10.1016/0019-1035(88)90162-5",
language = "English (US)",
volume = "75",
pages = "527--539",
journal = "Icarus",
issn = "0019-1035",
publisher = "Academic Press Inc.",
number = "3",

}

TY - JOUR

T1 - Particle properties and the large-scale structure of planetary rings

T2 - Rebound characteristics and viscosity

AU - Greenberg, Richard J.

PY - 1988

Y1 - 1988

N2 - In a swarm of particles on Keplerian orbits, like a planetary ring, systematic flow is circular with velocity decreasing with distance from the planet. Viscosity ordinarily transports momentum from a faster to a slower moving region, i.e., outward. But any individual at apocenter of its orbit moves slower, and at pericenter faster, than the mean flow, suggesting a reversed momentum transport or negative viscosity. Resolution of this seeming paradox illuminates the importance of physical properties of particles. A conventional model has uniform, highly elastic, perfectly slippery, spherical particles, with a particular dependence of elasticity on impact velocity. Even slight deviation from that ideal affects viscosity and leads to inconsistencies with observed ring structure. If particles are less elastic they may clump into large temporary agglomerations. The size of the larger bodies in the rings probably determines random velocities, viscosity, and much about ring structure.

AB - In a swarm of particles on Keplerian orbits, like a planetary ring, systematic flow is circular with velocity decreasing with distance from the planet. Viscosity ordinarily transports momentum from a faster to a slower moving region, i.e., outward. But any individual at apocenter of its orbit moves slower, and at pericenter faster, than the mean flow, suggesting a reversed momentum transport or negative viscosity. Resolution of this seeming paradox illuminates the importance of physical properties of particles. A conventional model has uniform, highly elastic, perfectly slippery, spherical particles, with a particular dependence of elasticity on impact velocity. Even slight deviation from that ideal affects viscosity and leads to inconsistencies with observed ring structure. If particles are less elastic they may clump into large temporary agglomerations. The size of the larger bodies in the rings probably determines random velocities, viscosity, and much about ring structure.

UR - http://www.scopus.com/inward/record.url?scp=0000638429&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0000638429&partnerID=8YFLogxK

U2 - 10.1016/0019-1035(88)90162-5

DO - 10.1016/0019-1035(88)90162-5

M3 - Article

AN - SCOPUS:0000638429

VL - 75

SP - 527

EP - 539

JO - Icarus

JF - Icarus

SN - 0019-1035

IS - 3

ER -