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[Programme]
Session 10: "Physical Properties of
Interplanetary Dust"
Date: Friday 8.30-11.50
Porous Flake Meteoroids and the Structure of
Small Bodies in the Solar System
B. Gustafson (Laboratory for Astrophysics,
Department of Astronomy,University of Florida,
Florida, USA; gustaf@astro.ufl.edu)
There is significant evidence that comets and
even some asteroids preserve in the structure of
their materials the physical dimensions of the
interstellar dust grains that they were made from.
Laboratory simulations of comet material in the
form of colloidal grains of a narrow size
distribution embedded in water ice produced thin
flakes from the process of sublimation. Simple
calculations show how the gas pressure below a
grain on the surface of a sublimating material
increases sharply as the layer of grains grows from
a monolayer to becoming two particles thick. This
is the probable cause for the formation of thin
flakes in the experiment and also on the surface of
comets under some circumstances. It probably
corresponds to one of several modes of dust and
meteoroid production from comets. I will review
some evidence for the presence of such flake-like
structures among dust and meteoroids. From the
external shape of dust aggregates, we will now turn
our attention to the internal structure of grain
arrangement. I will show how optical grain
properties including colour and polarization is
evidence for a hierarchy in the arrangement that
may be indicative of turbulence in the nebula at
the time of aggregation.. 10.1
Is the Problem of Sporadic Meteoroids Space
Distribution Solving Correct?
O.I. Belkovich (Zelenodolsk Branch of the Kazan
State University, Russia)
Nearly all that we know now on the distribution
in the interplanetary space of sporadic meteoroids
in the mass range from 0.00001 to 100000 g is based
mainly on the ground-based meteor observations. We
used to think that this problem was solved years
ago except for some details. I would say that it is
a delusion and I would like to prove that
assertion. Firstly. What variable or what variables
can represent the distribution of sporadic
meteoroids in the vicinity of some point of the
space? As a physicist I can say that it is the
phase density, i.e. density of particles in the
6-dimensional space of coordinates and velocities
as a function of their masses. What corresponds now
in the meteor astronomy to this definition?
Secondly. All ground-based meteor observations are
made on the moving and attracting Earth. Are you
sure that so-called astronomical selection taken
into account in processing of observed data is
correct? Thirdly. Most meteor astronomers like to
analyse their own observations and even in case of
some differences with the results of other
observations they are inclined to explanation of
those differences due to the different observed
masses of meteoroids. Do you believe them? 10.2
Clues to the Structure of Micrometeoroids,
from Dust Light Scattering Properties
A.Ch. Levasseur-Regourd, E. Hadamcik and
V. Haudebourg (Université Paris VI and
Service d'Aeronomie, CNRS-IPSL)
Knowing the size distribution and the shape
(compact or fluffy) of the dust particles in meteor
streams is of major importance, to understand their
mechanisms of interaction with the atmosphere and
their impacts effects on spacecraft. Some clues are
provided through observations of the solar light
scattered by cometary and interplanetary dust
particles. While their brightness and polarisation
phase curves are mostly similar, and indeed
characteristic of irregular particles, major
differences are noticed (both from remote and
in-situ observations) in terms of polarisation
levels and polarisation colours. These differences
correspond to different formation regions, and also
reveal an evolution of the dust morphological
properties, linked to fragmentation and evaporation
processes. Recent results from computational models
and laboratory measurements will be presented,
including polarisation phase curves of samples of
terrestrial or meteoritic origin, and results of
the CODAG experiment, launched from Esrange in May
1999. 10.6
Probing the Structure of the Interplanetary
Dust Cloud Using the AMOR Meteoroid Orbit Radar
David Galligan and Jack Baggaley
(University of Canterbury, Christchurch, New
Zealand)
During the past five years the University of
Canterbury's (New Zealand) Advanced Meteor Orbit
Radar (AMOR) has catalogued over half a million
high-quality meteoroid orbits. This data set, which
is greater in size than the combined total of all
previous surveys, provides high resolution
information on the structure of the dust cloud
orbiting the Sun. It is important to be able to
obtain an astronomically true picture of this dust
population for inclusion in interplanetary dust
models, as a background to studies of interstellar
dust such as that detected recently by W.J.
Baggaley, and from a general scientific interest
point of view. There are a series of selection
effects which must be allowed for in changing from
the orbital distributions as observed directly to
"true" distributions in space - these effects, and
the "corrected" distributions resulting from their
removal, will be discussed. 10.3
A Physical Model of the Sporadic Meteoroid
Complex
J. Jones, M. Campbell and S. Nikolova
(Department of Physics and Astronomy, University of
Western Ontario, London, Ontario, N6A 3K7
Canada)
Almost a half century ago Davies (1957) and
Hawkins and Southworth (1958) showed that the
directional distribution of the trajectories of
sporadic meteoroids is not isotropic. More recently
Jones and Brown (1993) showed that there are six
main clusters of sporadic meteor radiants for which
they determined the mean directions and widths. In
this paper we present the results of a model of the
evolution of sporadic meteoroid orbits which takes
long and short-period comets as the sources of
meteoric material and the Poynting-Robertson effect
as the dominant mechanism of orbital change. The
predicted radiant and orbital distributions are in
excellent agreement with observation. It is shown
that the inclusion of Steel and Elford's (1985)
estimate of the collisional lifetime of
meteoroid-sized particles, yields the observed
variation of the volume density of the particles
with distance from the Sun. 10.4
Lifetimes of Meteoroids in Interplanetary
Space: The Effect of Erosive and Catastrophic
Collisions
S. Nikolova, J. Jones (Department of
Physics and Astronomy, University of Western
Ontario, London, Ontario, N6A 3K7 Canada)
There are a number of mechanisms that affect the
lifetimes of meteoritic material in interplanetary
space. These include Poynting-Robertson effect,
Radiation Pressure, Electromagnetic forces and
collisions with other meteoritic particles. A
physical model of the sporadic meteoroid complex
was recently developed by Jones, Campbell and
Nikolova. The model considers short and long period
comets as primary sources of meteoritic material
and Poynting-Roberston effect as dominant mechanism
of orbital change. This paper investigates the
lifetimes of meteoroids against erosive and
catastrophic collisions including the effect of
orbital inclination using spatial density
distributions obtained by the latter model.
10.5
Microswarm Structure of a Meteoric Complex
outside of a Plane of an Ecliptic
Vladimir Sidorov, Sergey Kalabanov and
Tamara Filimonova (Kazan University)
Earlier we noted that the radiant distribution
of sporadic meteors obtained by the radar
tomography method shows stable structures of
radiants distributed along at particular elongation
angles from the apex. In the present activity we
have tried to find out (a) how these structures
vary in the course of the year, (b) how they are
correlated in time, and (c) whether they will be
repeated from one year to the next.
Nearly continuous radar observations of the
meteors from Kazan during January-April and
June-December 1993; during 3 different years in
April (1987,1988 and 1993); and in December
(1986-1988) were analysed by a quasi-tomographic
method with a bin size of 10 x 10 deg. We have
discovered that a toroidal structure dominates
February to April. During August to October, on the
contrary, a stable minimum is found in the
neighbourhoods of ± 90 deg to ecliptic plane.
The apparent distributions of meteors at different
angles to the cliptic plane during April for
different years are very close and mostly break up
into three maxima at 75, 90 and 115 deg. The data
of December and April were analysed additionally by
a discrete quasi-tomographic method with a 2 x 2
deg bin of radiant position. The role of showers
and microshowers in the formation of local stable
structures in the total radiant distributions of
meteors and a small comet origin of some of the
observed microshowers is discussed. PSB-17
Development of a New Reflectron Type TOF Mass
Spectrometer for Dust Analysis in Space
Yoshimi Hamabe (1), Sho Sasaki (1), Hideo
Ohashi (2), Tohru Kawamura (3), Ken-ichi Nogami 3),
Hajime Yano (4), Sunao Hasegawa (4), and Hiromi
Shibata (5)
1) Department of Earth and Planetary Science,
University of Tokyo; 2) Department of Ocean
Science, Tokyo University of Fisheries; 3)
Department of Physics, Dokkyo University School of
Medicine; 4) Institute of Space and Astronautical
Science; 5) High Fluence Irradiation Facility,
University of Tokyo
In order to analyze the elements of dust
particles in space, we have been developing a
reflectron-type dust TOF-MS (Time-Of-Flight Mass
Spectrometer) with a curved electric field. Now we
have done performance experiments of our device by
impacting hypervelocity microparticles with a Van
de Graaff accelerator at HIT (High Fluence
Irradiation Facility, University of Tokyo), where
carbon particles of 0.3-2.0 micrometer in diameter
are accelerated up to 5-20 km/s which is compared
to the velocity of dust particles in space. The
results showed the device has higher mass
resolution than the system with a parallel
reflecting region under the same experiment
situation by factor 2 or 3. Moreover the TOF
spectra showed the higher detection efficiency, and
the value was 10 times higher compared to the
parallel reflectron TOF-MS. These effective results
are considered to be caused by a curved electric
field in a reflecting region. PSB-18
Detection of Interplanetary and Interstellar
DUST particles by Mars Dust Counter (MDC) on Board
NOZOMI
Sho Sasaki (1), Eduard Igenbergs and Gerd
Hofschuster (2), Hideo Ohashi (3), Walter Naumann
(4), Ralf Muenzenmayer (5), Eberhard Gruen (6),
Yoshimi Hamabe (1), Heinrich Iglseder (7), Georg
Farber and Franz Fischer (2), Akira Fujiwara (8),
Tohru Kawamura and Ken-ichi Nogami (9), Tadashi
Mukai (10), Håkan Svedhem, Gerhard Schwehm
and Ingrid Mann (11)
1) Univ. Tokyo; 2) Technical Univ. Munich; 3)
Tokyo Univ. Fishery; 4) Kayser-Threde GmbH; 5)
Daimler-Benz Aerospace; 6) MPI-Kernphysik; 7)
Wilkhahn; 8) ISAS; 9) Dokkyo Univ. Medicine; 10)
Kobe Univ.; 11) ESA-ESTEC.
Mars Dust Counter (MDC) is an impact-ionization
dust detector on board the Japanese Mars mission
NOZOMI, which was launched on 1998-07-04. It is an
improved type of MDC-HITEN and MDC-BREMSAT and has
three detection channels (electron, iron, and
neutral) to discriminate noise signals from impact
signals. The main aim of MDC is to reveal the
predicted Martian ring or torus of dust from Phobos
and Deimos. On 1998-11-18, NOZOMI encountered the
Leonids meteoroid stream. MDC detected two dust
impacts, but directional analysis showed that those
particles probably did not belong to the Leonids.
However, the detected dust number in November 1998
was apparently higher than in other months. Leonids
meteoroid stream would have increased the dust
population around the Earth, probably though
collisions of stream particles with the Moon.
NOZOMI orbital plan was changed; Mars insertion was
postponed to be on 2004-01-01. Between 1999 and
2003, MDC-NOZOMI continuously measures the dust
environment between the Earth's and Martian orbits.
By the end of 2000, MDC had detected more than 60
events of dust impact. From the analysis of
velocity and direction of particles, those events
should include maybe five particles of interstellar
origin. 10.7
The Complex of Asteroids, Comets and
Meteoroids
Yu.I. Voloshchuk and B. L. Kashcheev
(Kharkiv State Technical University of
Radioelectronics, Lenin av., 14, Kharkiv, 61166,
Ukraine)
A global structure of the asteroid, comet, and
meteoroid complex and its origin is the objective
of this paper. The problem of
meteoroid-comet-asteroid evolution is considered on
the basis of modern studies of small bodies in the
Solar system. Along with major planets and their
satellites, the Solar system contains small bodies:
asteroids, comets, meteoroids and their complexes.
The bodies of these complex are in the state of
active evolution by perturbing forces, in contrast
to the stable systems of major planets and their
satellites. Another common feature of the bodies of
the complexes is their ability to fall to many
parts and to disintegrate. In addition, their
orbits pass partly through the same domains of
interplanetary space. There are classic the Taurid
asteroid complex, the complex of the Halley comet
with Aquarid and Orionid streams and many other
complexes in the Solar system. In general one
complex can include: several comets, several
asteroids and several decades of meteor streams.
Using one of the largest meteor data banks and the
results of calculation of asteroid orbit evolution,
new approaches to the search for space bodies that
may be the parents' bodies of the meteor streams
are formulate. More than 230000 individual orbits
of meteoroids with masses exceeding 10-6 g were
registered by the meteor automatic radar system
(MARS) from January 1972 till December 1978 in
Kharkiv. 159787 individual orbits were chosen
according to special technique to increase further
analysis reliability. The technique for selection
of streams and associations from a large sample of
individual meteor orbits is used. The investigation
were made on the different samples from observation
material, which volume is more than 5 thousands
minor meteor showers of this unique Kharkiv
electronic orbit catalogue. PSB-19
Io Revealed in the Jovian Dust
Streams
Amara L. Graps (1), Eberhard Gruen (1),
Harald Krueger (1), Mihaly Horanyi (2), Håkan
Svedhem (3) and the Galileo and Cassini Dust
Science Teams
1) Max-Planck-Institut für Kernphysik,
Heidelberg, Germany; 2) LASP, Boulder, USA; 3)
European Space Research and Technology Centre,
Noordwijk,The Netherlands
The Jovian dust streams are high-rate (at least
250 km/s) bursts of submicron-sized particles
travelling in the same direction from a source in
the Jovian system. The source of the Jovian dust
streams is Jupiter's moon, Io, in particular, dust
from Io's volcanoes. Charged Io dust, travelling on
trajectories from Io's location, is shown to have
some particular signatures in real space, in
frequency space, inside of Jupiter's magnetosphere,
and outside of Jupiter's magnetosphere. The work
presented here describes an emerging
electrodynamical picture of the Jovian dust streams
as they appear inside and outside of the Jupiter
environment using data from the Galileo spacecraft
in years 1996-2000 and from the Galileo-Cassini
December 2000 dust stream measurements. We show
that some aspects of the dust stream particles'
dynamics in real space can be understood if the
particles charges are a varying parameter in the
force equation. The Jovian dust stream dynamics in
the frequency-transformed Galileo dust measurements
show two different signatures, depending whether
the dust detector is located outside of the Jovian
magnetosphere or inside of the Jovian
magnetosphere. This time-frequency analysis is the
first direct evidence that Io is the source of the
Jovian dust streams. 10.8
Components of a New Interplanetary Meteoroid
Model
V. Dikarev (1,4), E. Gruen (1), M.
Landgraf (2), J. Baggaley (3), D.P. Galligan
(3)
1) Max-Planck-Institut für Kernphysik,
Heidelberg, Germany; 2) European Space Operations
Centre, Darmstadt, Germany; 3) University of
Canterbury, Christchurch, New Zealand; 4)
Astronomical Institute of St. Petersburg State
University, Russia
New populations of interplanetary dust are
proposed for the new ESA interplanetary meteoroid
model. Formulation of the model and its populations
differ from those adopted in earlier meteoroid
models and are tied to long-term dynamics of the
interplanetary dust. To validate the new model,
infrared emission observations with COBE DIRBE
instrument, impact counts with the dust detectors
aboard Galileo and Ulysses spacecraft, and the
radar meteors monitored with AMOR are used.
10.9
Dust Measurements in the Geostationary
Orbit
Håkan Svedhem and Gerhard
Drolshagen (ESA/ESTEC, PB 299, NL-2200AG Noordwijk,
The Netherlands; h.svedhem@esa.int and
gerhard.drolshagen@esa.int) and Eberhard Gruen (MPI
f Kernphysik, D-69029 Heidelberg, Germany;
eberhard.gruen@mpi-hd.mpg.de)
The impact detector GORID, on the Russian
Express II satellite has now collected data on
Cosmic Dust and Space Debris for more than four
years from its geostationary location at first 80
and later 103 deg East. During this time a large
number of events have been registered and these are
now being analysed and categorised. The yearly
average number of certain impacts has varied from
1.7 per day to 3.2 per day. Recent re-calibration
of a spare model has resulted in more accurate
factors for conversion of the measured parameters
into physical parameters as particle mass and
velocity. Data sets from one or several full years
are used to suppress the possible biases that can
result from spatial, temporal and directional
variations in the flux and to reduce the
statistical errors. During several occasions
particles have been detected clustered in time,
with up to 30 or more particles within one hour. In
addition, at some dates these clusters have been
detected at the same times for several consecutive
dates. We believe these particles are related to
exhaust particles from the solid rocket boosters
used for changing the geostationary transfer orbit
into a geostationary orbit. For the remaining
particles the majority seems to be natural
meteoroids. 10.10
Cosmic Dust near 1 AU
Ingrid Mann (1, 2), Hakan Svedhem (1),
Sho Sasaki (3), Eduard Igenbergs (4), Gerd
Hofschuster (4), Walter Naumann (4), and Hideo
Ohashi (5)
1) ESA Space Science Department, ESTEC,
Noordwijk, The Netherlands; 2) Institute of
Planetology, The University of Muenster, Germany;
3) The University of Tokyo, Japan; 4) Fachgebiet
Raumfahrttechnik, TU Munich, Germany; 5) Tokyo
University of Fisheries, Japan
Cosmic dust near 1 AU results from the collision
evolution of dust produced from comets, asteroids
and meteoroids. Moreover, dust particles entering
the solar system from interstellar space are
detected near the Earth orbit. Knowledge of the
size distribution and of the orbital distribution
of dust near 1 AU therefore helps to understand the
sources of the dust cloud as well as its collision
evolution. We discuss the velocity distribution of
dust near 1 AU as well as the collision evolution
of dust and the production of beta-meteoroids that
leave the solar system in hyperbolic orbits.
Moreover we discuss the expected flux of
interstellar dust and its gravitational focussing.
We finally refer to dust measurements of the Mars
Dust Counter experiment onboard the Japanese
mission Nozomi that works since 1998. Nozomi
measurements near Earth have detected particles
with masses 10^-17 kg < m < 10^-12 kg. The
Nozomi measurement planned during the next phase of
the mission will provide dust fluxes between about
1 and 1.6 AU. PSB-20
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