33 research outputs found
Debris disk size distributions: steady state collisional evolution with P-R drag and other loss processes
We present a new scheme for determining the shape of the size distribution,
and its evolution, for collisional cascades of planetesimals undergoing
destructive collisions and loss processes like Poynting-Robertson drag. The
scheme treats the steady state portion of the cascade by equating mass loss and
gain in each size bin; the smallest particles are expected to reach steady
state on their collision timescale, while larger particles retain their
primordial distribution. For collision-dominated disks, steady state means that
mass loss rates in logarithmic size bins are independent of size. This
prescription reproduces the expected two phase size distribution, with ripples
above the blow-out size, and above the transition to gravity-dominated
planetesimal strength. The scheme also reproduces the expected evolution of
disk mass, and of dust mass, but is computationally much faster than evolving
distributions forward in time. For low-mass disks, P-R drag causes a turnover
at small sizes to a size distribution that is set by the redistribution
function (the mass distribution of fragments produced in collisions). Thus
information about the redistribution function may be recovered by measuring the
size distribution of particles undergoing loss by P-R drag, such as that traced
by particles accreted onto Earth. Although cross-sectional area drops with
1/age^2 in the PR-dominated regime, dust mass falls as 1/age^2.8, underlining
the importance of understanding which particle sizes contribute to an
observation when considering how disk detectability evolves. Other loss
processes are readily incorporated; we also discuss generalised power law loss
rates, dynamical depletion, realistic radiation forces and stellar wind drag.Comment: Accepted for publication by Celestial Mechanics and Dynamical
Astronomy (special issue on EXOPLANETS
Chirikov Diffusion in the Asteroidal Three-Body Resonance (5,-2,-2)
The theory of diffusion in many-dimensional Hamiltonian system is applied to
asteroidal dynamics. The general formulations developed by Chirikov is applied
to the Nesvorn\'{y}-Morbidelli analytic model of three-body (three-orbit)
mean-motion resonances (Jupiter-Saturn-asteroid system). In particular, we
investigate the diffusion \emph{along} and \emph{across} the separatrices of
the (5,-2,-2) resonance of the (490) Veritas asteroidal family and their
relationship to diffusion in semi-major axis and eccentricity. The estimations
of diffusion were obtained using the Melnikov integral, a Hadjidemetriou-type
sympletic map and numerical integrations for times up to years.Comment: 27 pages, 6 figure
Galileo dust data from the jovian system: 2000 to 2003
The Galileo spacecraft was orbiting Jupiter between Dec 1995 and Sep 2003.
The Galileo dust detector monitored the jovian dust environment between about 2
and 370 R_J (jovian radius R_J = 71492 km). We present data from the Galileo
dust instrument for the period January 2000 to September 2003. We report on the
data of 5389 particles measured between 2000 and the end of the mission in
2003. The majority of the 21250 particles for which the full set of measured
impact parameters (impact time, impact direction, charge rise times, charge
amplitudes, etc.) was transmitted to Earth were tiny grains (about 10 nm in
radius), most of them originating from Jupiter's innermost Galilean moon Io.
Their impact rates frequently exceeded 10 min^-1. Surprisingly large impact
rates up to 100 min^-1 occurred in Aug/Sep 2000 when Galileo was at about 280
R_J from Jupiter. This peak in dust emission appears to coincide with strong
changes in the release of neutral gas from the Io torus. Strong variability in
the Io dust flux was measured on timescales of days to weeks, indicating large
variations in the dust release from Io or the Io torus or both on such short
timescales. Galileo has detected a large number of bigger micron-sized
particles mostly in the region between the Galilean moons. A surprisingly large
number of such bigger grains was measured in March 2003 within a 4-day interval
when Galileo was outside Jupiter's magnetosphere at approximately 350 R_J
jovicentric distance. Two passages of Jupiter's gossamer rings in 2002 and 2003
provided the first actual comparison of in-situ dust data from a planetary ring
with the results inferred from inverting optical images.Comment: 59 pages, 13 figures, 6 tables, submitted to Planetary and Space
Scienc
Influence of fast interstellar gas flow on dynamics of dust grains
The orbital evolution of a dust particle under the action of a fast
interstellar gas flow is investigated. The secular time derivatives of
Keplerian orbital elements and the radial, transversal, and normal components
of the gas flow velocity vector at the pericentre of the particle's orbit are
derived. The secular time derivatives of the semi-major axis, eccentricity, and
of the radial, transversal, and normal components of the gas flow velocity
vector at the pericentre of the particle's orbit constitute a system of
equations that determines the evolution of the particle's orbit in space with
respect to the gas flow velocity vector. This system of differential equations
can be easily solved analytically. From the solution of the system we found the
evolution of the Keplerian orbital elements in the special case when the
orbital elements are determined with respect to a plane perpendicular to the
gas flow velocity vector. Transformation of the Keplerian orbital elements
determined for this special case into orbital elements determined with respect
to an arbitrary oriented plane is presented. The orbital elements of the dust
particle change periodically with a constant oscillation period or remain
constant. Planar, perpendicular and stationary solutions are discussed.
The applicability of this solution in the Solar system is also investigated.
We consider icy particles with radii from 1 to 10 micrometers. The presented
solution is valid for these particles in orbits with semi-major axes from 200
to 3000 AU and eccentricities smaller than 0.8, approximately. The oscillation
periods for these orbits range from 10^5 to 2 x 10^6 years, approximately.Comment: 22 pages, 3 figures; Accepted for publication in Celestial Mechanics
and Dynamical Astronom
Motion of dust in mean-motion resonances with planets
Effect of stellar electromagnetic radiation on motion of spherical dust
particle in mean-motion orbital resonances with a planet is investigated.
Planar circular restricted three-body problem with the Poynting-Robertson (P-R)
effect yields monotonous secular evolution of eccentricity when the particle is
trapped in the resonance. Elliptically restricted three-body problem with the
P-R effect enables nonmonotonous secular evolution of eccentricity and the
evolution of eccentricity is qualitatively consistent with the published
results for the complicated case of interaction of electromagnetic radiation
with nonspherical dust grain. Thus, it is sufficient to allow either nonzero
eccentricity of the planet or nonsphericity of the grain and the orbital
evolutions in the resonances are qualitatively equal for the two cases. This
holds both for exterior and interior mean-motion orbital resonances. Evolutions
of longitude of pericenter in the planar circular and elliptical restricted
three-body problems are shown. Our numerical integrations suggest that any
analytic expression for secular time derivative of the particle's longitude of
pericenter does not exist, if a dependence on semi-major axis, eccentricity and
longitude of pericenter is considered (the P-R effect and mean-motion resonance
with the planet in circular orbit is taken into account).
Change of optical properties of the spherical grain with the heliocentric
distance is also considered. The change of the optical properties: i) does not
have any significant influence on secular evolution of eccentricity, ii) causes
that the shift of pericenter is mainly in the same direction/orientation as the
particle motion around the Sun. The statements hold both for circular and
noncircular planetary orbits.Comment: 22 pages, 12 figure
The Kuiper Belt and Other Debris Disks
We discuss the current knowledge of the Solar system, focusing on bodies in
the outer regions, on the information they provide concerning Solar system
formation, and on the possible relationships that may exist between our system
and the debris disks of other stars. Beyond the domains of the Terrestrial and
giant planets, the comets in the Kuiper belt and the Oort cloud preserve some
of our most pristine materials. The Kuiper belt, in particular, is a
collisional dust source and a scientific bridge to the dusty "debris disks"
observed around many nearby main-sequence stars. Study of the Solar system
provides a level of detail that we cannot discern in the distant disks while
observations of the disks may help to set the Solar system in proper context.Comment: 50 pages, 25 Figures. To appear in conference proceedings book
"Astrophysics in the Next Decade
Origin and Evolution of Saturn's Ring System
The origin and long-term evolution of Saturn's rings is still an unsolved
problem in modern planetary science. In this chapter we review the current
state of our knowledge on this long-standing question for the main rings (A,
Cassini Division, B, C), the F Ring, and the diffuse rings (E and G). During
the Voyager era, models of evolutionary processes affecting the rings on long
time scales (erosion, viscous spreading, accretion, ballistic transport, etc.)
had suggested that Saturn's rings are not older than 100 My. In addition,
Saturn's large system of diffuse rings has been thought to be the result of
material loss from one or more of Saturn's satellites. In the Cassini era, high
spatial and spectral resolution data have allowed progress to be made on some
of these questions. Discoveries such as the ''propellers'' in the A ring, the
shape of ring-embedded moonlets, the clumps in the F Ring, and Enceladus' plume
provide new constraints on evolutionary processes in Saturn's rings. At the
same time, advances in numerical simulations over the last 20 years have opened
the way to realistic models of the rings's fine scale structure, and progress
in our understanding of the formation of the Solar System provides a
better-defined historical context in which to understand ring formation. All
these elements have important implications for the origin and long-term
evolution of Saturn's rings. They strengthen the idea that Saturn's rings are
very dynamical and rapidly evolving, while new arguments suggest that the rings
could be older than previously believed, provided that they are regularly
renewed. Key evolutionary processes, timescales and possible scenarios for the
rings's origin are reviewed in the light of tComment: Chapter 17 of the book ''Saturn After Cassini-Huygens'' Saturn from
Cassini-Huygens, Dougherty, M.K.; Esposito, L.W.; Krimigis, S.M. (Ed.) (2009)
537-57
Understanding Asteroid Regolith Properties Using Solar System Dust Bands
Following the discovery of the first young, still forming, partial zodiacal dust band, we have shown that partial bands retain significant information about both the size-frequency distribution and cross-sectional area of dust released in the disruption of their parent asteroids. The new observational constraints to our modeling work that are provided by the partial dust band allow us to begin to reconstruct the properties of the regolith on the surface of the parent asteroid before its collisional disruption, including the depth of the regolith and the size-distribution of the particles present. Using the constraints provided by modeling the partial dust band at 17°, we discuss the surface regolith of the parent asteroid to the Emilkowalski cluster and investigate the relationship between regolith depth and the size distribution of particles. By examining the available data for other asteroids, we determine a scaling relationship between depth of regolith and asteroid size