3. WORK PROGRAMME
3.1 Research Project
3.1.1 Title
Theoretical and experimental investigations of light scattering by
heterogeneous non-spherical cosmic dust grains.
3.1.2 Objectives
The project is aimed at the development of a new generation of cosmic dust
models and the creation of tools required in light scattering and radiative
transfer. There are five major tasks to be solved:
1. Development of new exact and approximate theoretical methods to calculate
scattering of radiation by particles of different shapes and structures.
Critical analysis of the various approaches in the field of light scattering
by small particles and the determination of the area of their applicability.
2. Laboratory measurements of light scattering characteristics (including
elements of scattering matrix) for particles of various sizes, shapes,
compositions and structure and a detailed comparison of the theory with
experiments.
3. Creation of an electronic database containing as benchmarks the optical
properties obtained for the particles by experimental and theoretical
methods, the light scattering codes realizing both exact and approximate
approaches, references to papers and other related information.
4. Development of numerical codes to simulate polarized radiation transfer
in media of arbitrary geometry in the cases of single and multiple
scattering by non-spherical aligned particles.
5. Applications of the techniques developed to interpretation of the recent
astrophysical observations of interstellar, circumstellar, interplanetary
dust; development of new models of cosmic dust grains as composite
non-spherical particles.
3.1.3 Background & Justification for Undertaking the Project
Dust is present in most cosmic objects from the Solar system to nuclei of
distant active galaxies, and practically everywhere the dust grains play
an important role in physics and chemistry of the interstellar matter.
In contrast, the parameters of the dust grains are still not well known, and
this prevents the development of physical and evolutionary models of the
objects.
Our knowledge on the cosmic dust is mainly gained from the analysis of its
interaction with radiation, which is usually grounded on the theory of light
scattering by small particles. This theory is also widely used in atmospheric
and ocean optics, biophysics, colloidal chemistry, radiophysics as well as
in numerous industrial applications.
In recent years good progress in theoretical and experimental studies of
light scattering by non-spherical particles has been made (see Proceedings
of the conferences held since 1995 in Amsterdam, Bremen, Helsinki, Moscow,
New York, Vigo). Nevertheless, interpretation of the astronomical data is
still based on the Lorenz-Mie theory for homogeneous isotropic spheres.
However, this model cannot explain many astrophysical observations
which indicate the existence of non-spherical, heterogeneous and compounded
dust grains in interstellar clouds, circumstellar shells, and the interplanetary
medium.
General methods to calculate light scattering by particles of an arbitrary
shape and structure (e.g., the Discrete Dipole Approximation) are extremely
time-consuming, which significantly complicates their application to modelling
of astrophysical objects where the grain size distribution and the
multi-wavelength radiation of sources must be taken into account. More
specialized methods (e.g. Separation of Variables and T-matrix methods)
also should be modified to become more applicable.
The feature of astrophysical problems is that we know the nature of cosmic
grains only approximately. In some cases the real structure of the grains is
not very important and their optical properties can be well described by the
Effective Medium Theory (EMT) that replaces a heterogeneous particle by
homogeneous one with an effective refractive index. Up to now the applications
of the EMT to astrophysics were limited only by a few standard mixing rules
for 2-3 components.
In the frame of the project it is planned to compare various exact and
approximate approaches to light scattering calculations and to give
recommendations on their use in different situations. There were a few
attempts to compare some of the approaches (e.g., J.W. Hovenier et al.,
J. Quant. Spectrosc. Rad. Transfer, v. 55, 695, 1996; Th. Wriedt &
U. Comberg, J. Quant. Spectrosc. Rad. Transfer, v. 60, 411, 1998),
but many existing needs are definitely not satisfied.
It is very difficult to calculate the scattering properties of irregularly
shaped and compounded particles and here experimental techniques can help
to solve the problem. Light scattering measurements are made in a laser
beam (e.g., by J.W. Hovenier and his co-workers) or using microwave analogues
(by K.H. Zerull, B.A.S. Gustafson), and although the first results for
aggregate particles have been recently obtained, the number of possible
applications of the technique is still very large.
The significance of both experimental and theoretical results increases
if there is a modern tool of data distribution like an electronic database
with an access via the Internet. Such a database on optical properties of
small particles is absent in the World Wide Web.
In many astrophysical applications (circumstellar shells, nebulae, etc.)
the effects of optical thickness on (polarized) radiation transfer are
very important. The method which can be applied in these situations to
a complex geometry of scatterers is Monte Carlo simulations (along with the
scattering theory). However, till now the realistic case of non-spherical
aligned particles was never considered in such a modelling.
There are a number of gaps in modelling of cosmic dust grains and interpretation
of their observed manifestations (interstellar extinction and polarization,
thermal infrared and polarized scattered radiation, solid features in spectra,
etc.). For instance, the recent observations of the interstellar linear
polarization in the infrared (about 2-5 micron) and ultraviolet (about 0.13-0.30
micron) spectral regions have greatly enlarged our knowledge about the
wavelength dependence of the polarization (see, e.g., P.G. Martin et al.,
Astrophys. J., v. 392, 691, 1992; Astrophys. J., v. 510, 905, 1999). However,
there is still a gap in the interpretation of these data since inhomogeneous
non-spherical particles of finite sizes have not yet been applied.
The launch of the Infrared Space Observatory (ISO) has opened the 2-200
micron spectral region for quantitative solid state spectroscopy which, in
particular, has led to discovery of many narrow emission features
attributed to crystalline silicates. These silicates are found in the dust
shells of young stars and evolved red giants and supergiants (L.B.F.M. Waters
et al., Solid Interstellar Matter: the ISO Revolution, 1999, p. 219). A detailed
consideration of the processing of grains in outflows of oxygen-rich stars and
their further evolution has not yet been performed.
Polarimetric studies of the solar light scattered by cometary dust
grains have been made at various phase angles alpha (alpha = 0, if the Sun,
the Earth and a comet are located in a line, i.e. the solar radiation
backscattered by cometary dust is observed). They have provided information
on the properties of the dust grains released from the cometary nucleus.
The detected circular polarization of the P/Halley comet (K. Metz &
R. Haefner, Astron. Astrophys., v. 187, 539, 1987) and the non-zero linear
polarization of some other comets at alpha = 0 (see N.N. Kiselev, Astron.
Vestn., v. 53, 181, 1999 for a review) undoubtedly indicate that the cometary
grains are non-spherical and should be partly aligned. Nevertheless, these
circumstances were not taken into account in the models of cometary dust.
The observed phase dependence of the linear polarization of light scattered
by Saturn's rings shows a narrow peak of negative polarization which can be
explained in frames of the theory of coherent backscattering (V.K. Rosenbush
et. al., Astrophys. J., v. 487, 402, 1997). This theory was developed for
point-like scatterers, and in order to obtain information on the Saturn's
rings particles, one needs a coherent backscattering model in which the
finite size of scatterers would be taken into account.
The above-mentioned problems are only a part of those planned to be considered
within the project.
3.1.4 Scientific/Technical Description
3.1.4.1 RESEARCH PROGRAMME
Task 1 (Light scattering theory)
T1.1 Creation of stable algorithms and new computer codes as well as
modification of earlier developed codes to calculate the optical properties
for the following kinds of particles: homogeneous and core-mantle
spheroids, axisymmetric particles, multi-layered spheres and cylinders,
etc.
T1.2 Study of internal radiation fields for particles of various shapes and
compositions; consideration of partial evaporation (formation of voids)
and destruction of irradiated particles.
T1.3 Development of approximate methods applicable in different ranges of
parameter values, namely: quasistatic and Rayleigh approximations for
multi-layered scatterers, anomalous diffraction approximation (in the
vector case), ray optics approximation for inhomogeneous particles.
T1.4 Construction of new mixing rules and analysis of various Effective Medium
Theories (in particular, a comparison with calculations made by Discrete
Dipole Approximation codes) in the case of multi-component particles.
T1.5 A detailed comparison of exact and approximate methods and determination of
the range of validity of different approximations.
General output - the numerical realizations of a series of new exact and
approximate methods in light scattering by small particles and a description
of the area of parameter space where these and other methods are accurate.
The results will provide a basis for the work on other tasks of the project.
Novelty - the new computational tools will further extend the applicability
of the light scattering theory.
Risks - there is an inevitable risk that some of the new algorithms will not
be much more efficient than older ones and that new mixing rules of the EMTs
will not have larger applicability ranges and accuracy.
Participants - P2, P3, P4 (coordinator), P5, P6.
Schedule - months 1-24.
(for more details of the two last items, see 3.1.6.1)
Notes on T1.1:
inputs - a collection of the light scattering codes developed earlier by
the participants (P2, P3, P4, P5, P6);
methods - the codes to be written will be based on special versions of
Separation of variables method in spherical, cylindrical and spheroidal
coordinate systems (see, e.g., Voshchinnikov & Mathis, Astrophys. J., 1999,
v. 526, N1 - see the LANL-preprint astro-ph/9908240; Farafonov et al., Appl.
Opt., v .35, 5412, 1996); new approaches to the T-matrix method (e.g.,
Farafonov et al., J. Quant. Spectrosc. Rad. Transfer, v. 63, 205, 1999); new
method of variational boundary conditions (Petrov & Babenko, J. Quant.
Spectrosc. Rad. Transfer, v. 63, 237, 1999) and others;
outputs - a series of new codes in Fortran 90 with full documentations and
papers presenting the new algorithms and codes.
Notes on T1.2:
inputs - computer codes earlier created by the team in Minsk (P4);
methods - solution to the heat conduction equation, determination of dynamics
of temperature fields and so on (see Astafieva & Babenko, J. Quant. Spectrosc.
Rad. Transfer, v. 63, 459, 1999 and references therein);
outputs - new software to solve the problem for cosmic physical conditions.
Notes on T1.3:
inputs - approaches and codes developed earlier in Minsk (P4), Kharkov (P5),
Petersburg (P6);
methods - see, e.g., Perel'man, Appl. Opt., 30, 475, 1991; Kokhanovsky, Optics
of Light Scattering Media, Wiley, 1999;
outputs - computer codes and papers describing capacities of the new methods.
Notes on T1.4:
inputs - light scattering codes to be developed in T1.1 and some other codes;
methods - see, e.g., Stognienko, Henning & Ossenkopf, Astron. Astrophys.,
v. 296, 797, 1995; Voshchinnikov & Mathis, Astrophys. J., 1999, v. 526, N1 -
the LANL-preprint astro-ph/9908240;
outputs - computer programs in Fortran 90 and conclusions on the range of
applicability and accuracy of the new rules.
Notes on T1.5:
inputs - the programs to be developed in T1.1, T1.3, T1.4 and many other codes;
methods - exact and approximate approaches (codes) will be confronted in the
four-dimensional parameter space (refractive index, diffraction parameter,
and parameters describing the shape and inhomogeneity of particles);
outputs - published review(s) on the results of the comparison.
Task 2 (Light scattering experiments)
T2.1 Measurements of the extinction cross-sections and scattering matrix for
analogues of cosmic dust grains including inhomogeneous, porous, and
composite particles.
T2.2 Comparison of data on light scattering by small particles measured in
laboratories by different techniques.
T2.3 Analysis of distinctions between the data obtained from the experiments and
theoretical calculations and a search for the best analytical models
reproducing experimental data.
General output - a set of experimentally obtained data on the characteristics
of light scattered by particles of different kinds. The data will be used in
the planned applications (T5.2, T5.3, T5.4) and are especially important for
large size particles when the exact methods meet problems and the
approximations for large particles do not yet work as well as for particles
of a complex structure.
Novelty - the new experimental data will extend knowledge on the scattering
properties of large particles of complex structure.
Risk - problem of control of the quality of industrial samples.
Participants - P1, P2 (coordinator), P3, P4, P5, P6.
Schedule - months 1-24.
Notes on T2.1:
inputs - special samples and the equipment of the Jena (P2) and Kharkov (P5)
laboratories (some measurements may be made also with the equipment of the
Free University, Amsterdam);
methods - direct measurements of the characteristics of light scattered by
submicron particles;
outputs - a large set of data for a variety of particle kinds, including data
to be used in T3.2 and the planned applications (see below).
Notes on T2.2:
inputs - results to be obtained in T2.1 and other data available in the
literature;
methods - measurements for simple samples (spheres, spheroids, etc.);
outputs - conclusions on reliability of the experimental data and a set of
well-checked data for the database to be created.
Notes on T2.3:
inputs - results to be obtained in T2.1 and tested in T2.2 and the codes to be
developed in T1.1, T1.3 as well as some other codes;
methods - consideration in a wide range of parameter values;
outputs - paper(s) with the results of the comparison and recommendations for
different applications (including T5.1, T5.2, T5.3, T5.4).
Task 3 (Electronic database)
T3.1 Computation of thoroughly checked benchmark results (various
cross-sections and elements of scattering matrix calculated at least by two
different methods) for homogeneous/inhomogeneous spherical/non-spherical
particles in a wide range of parameter values.
T3.2 Creation of a large library of the optical properties obtained by
experimental and theoretical methods for particles of various shapes,
sizes, compositions, structures, etc.
T3.3 Development of an electronic database of optical properties and its
filling with original codes, the benchmark results, and the data library as
well as references to papers on the subject and links to related Internet
resources.
General output - the Database of Optical Properties (DOP) which will allow
investigators to solve a wide spectrum of problems in various scientific
and industrial applications of light scattering as well as will serve as
an educational tool for high schools.
Novelty - there are no analogues of the DOP in the Internet.
Risks - none.
Participants - P1, P2, P3 (coordinator), P4, P5, P6.
Schedule - months 13-30.
Notes on T3.1:
inputs - the codes to be developed in T1.1, T1.3, T1.4 and other available light
scattering codes;
methods - the data will be accepted as a bookmark provided two or more codes
realizing different approaches give the same result;
outputs - the tables (and plots) of different cross-sections and elements of
scattering matrix.
Notes on T3.2:
inputs - the optical properties to be measured in laboratories (T2.1, T2.2)
and calculated by different codes including those to be developed in T1.1;
methods - use of special graphics software;
outputs - series of tables and plots in GIF and PostScript formats showing the
optical properties of particles.
Notes on T3.3:
inputs - the codes to be developed in T1.1, T1.3, T1.4; the results to be
obtained in T1.5, T2.3, T3.1; the library from T3.2;
methods - use of database organization standards and special tools such as Java
and Perl computer languages, CGI-interfaces, MS FrontPage, etc.
output - an electronic database with a free access via the Internet.
Task 4 (Polarized radiation transfer)
T4.1 Creation of a numerical code (based on Monte Carlo simulations) to
calculate the transfer of polarized radiation and the spectral energy
distribution for non-spherical aligned particles arbitrarily distributed
around one or several illuminating sources.
T4.2 Development of efficient models based on single light scattering by
non-spherical particles and allowing to calculate intensity and
polarization of radiation escaping from a medium of arbitrary geometry;
T4.3 Creation of a model of the opposition effects (the enhanced backscattering
of light and polarization effects at small phase angles) for closely
packed media based on interference of double scattered waves.
General output - a number of tools for numerical simulations of polarized
radiation transfer in media populated by aligned non-spherical dust grains.
The tools are required for interpretation of the modern polarimetric
observations of complex objects like circumbinary dust discs made with high
angular resolution. The single-scattering models will be applied to check
the general Monte Carlo code and to interpret the observations of optically
thin objects.
Novelty - the code for numerical simulations of polarized radiation transfer
in dusty media with anisotropic optical properties will be the unique one.
Risks - none.
Participants - P1, P2, P3 (coordinator), P5.
Schedule - months 1-24.
Notes on T4.1:
inputs - Monte Carlo codes earlier developed in Jena (P2) and Petersburg (P3);
methods - numerical simulation of light scattering taking into account all
elements of scattering matrix as they are non-zero for non-spherical aligned
particles;
outputs - a Monte Carlo code with full documentation and a paper presenting
the code and its testing.
Notes on T4.2:
inputs - single-scattering codes created in Petersburg (P3);
methods - numerical simulations of light scattering taking into account all the
elements of scattering matrix;
outputs - new codes with full documentation.
Notes on T4.3:
inputs - software developed in Kharkov (P5);
methods - the double scattering approximation (see Tishkovets et al., J. Quant.
Spectrosc. Rad. Transfer, v. 61, 767, 1999);
outputs - a new code in Fortran 90 with documentation.
Task 5 (Astrophysical applications)
T5.1 Development of new models of interstellar dust grains (heterogeneous
particles with tight constraints on element abundances) and their
application to interpretation of interstellar extinction and polarization
and other data.
T5.2 Interpretation of observational data obtained for the shells around evolved
and young stars with the ISO and other instruments (including polarization
maps) in the frame of the model of composite circumstellar grains taking
into account the partial recrystallization of amorphous silicates.
T5.3 Development of a new approach to cometary grains basing on inhomogeneous
non-spherical particles and a simultaneous interpretation of observational
data on stellar occultations by comets, their polarization phase curves
and infrared fluxes.
T5.4 Interpretation of the phase dependence of polarization observed for
Saturn's rings in the frame of a coherent backscattering model.
General outputs - new insight into the nature of interstellar, circumstellar,
and interplanetary dust grains.
Novelty - new generation of models of the cosmic grains as finite size
non-spherical heterogeneous particles; detailed consideration of thermal
history of circumstellar and cometary dust grains; the first simultaneous
interpretation of data on scattering, extinction and absorption properties
of cometary dust grains; a new approach to investigation of dust particles
in Saturn's rings and so on.
Risks - inadequate treatment of grain alignment and magnetic fields in cosmic
objects; complexity of inverse task solution caused by large dimension of
parameter space and not well known nature of the dust grains.
Participants - P1 (coordinator), P2, P3, P4, P5.
Schedule - months 7-30.
Notes on T5.1:
inputs - light scattering codes to be developed in T1.1, T1.3, T1.4; special
software created earlier in Minsk (P4); available observational data;
methods - a direct comparison of calculations with the data as well as
solution of the inverse task using the approach of Oshchepkov et al.,
Geophys. Res. Lett., 1999, in press;
outputs - estimates of cosmic dust grain characteristics on the base of
heterogeneous particle models explaining almost all features detected
by recent observations of interstellar extinction and polarization.
Notes on T5.2:
inputs - the light scattering codes to be developed in T1.1, T1.3, T1.4; the
code and analysis from T1.2; the experimental data from T3.1; the radiative
transfer codes (T4.1, T4.2); different observational data;
methods - a detailed consideration of the partial recrystallization of amorphous
silicate grains in the vicinities of stars, calculations of the optical
properties of inhomogeneous particles by the exact or approximate methods,
modelling of polarized radiation transfer, fitting of the observational
data available for different objects;
outputs - estimates of characteristics of dust grains and of their spatial
distribution around evolved and young stars basing on the model of composite
non-spherical particles.
Notes on T5.3:
inputs - the light scattering codes to be developed in T1.1, T1.3, T1.4; the
code and analysis from T1.2; the experimental data from T3.1; the radiative
transfer codes (T4.2); different observational data;
methods - determination of the physical properties of cometary grains taking
into account their thermal history in dependence on the distance from the
Sun, calculations of the optical properties of inhomogeneous particles,
modelling of polarized radiation transfer in the single scattering
approximation, confrontation of the results of calculations and observations;
outputs - results of simultaneous interpretation of observed stellar occultations
by comets, their polarization phase curves and infrared fluxes (to be made
with inhomogeneous non-spherical particles) and estimates of cometary grain
characteristics.
Notes on T5.4:
inputs - the results obtained in T4.3; data of polarimetric observations of
Saturn's rings;
methods - the double scattering approximation, modelling of polarized radiation
transfer, comparison of calculations with the observational data;
outputs - estimates of the properties and concentration of dust particles in
Saturn's rings.
3.1.4.2 DELIVERABLES, EXPLOITATION & DISSEMINATION OF RESULTS
An intermediate report will be sent to the INTAS after 15 months of work when
the main results in the Tasks 1, 2 and 4 should be obtained and the activity
in the Tasks 3 and 5 should give first results. A final report will be sent at
the end of work. The reports will be supplied by a detailed description of the
products of the work: algorithms and codes to be created, papers and reviews
to be published, models to be developed, and database to be made.
The results which are planned to be obtained within the project will be
presented at the international astronomical and optical conferences to be held
in 2001 and 2002.
The results will be also published in the international journals like Journal
of Quantitative Spectroscopy & Radiative Transfer, Astronomy & Astrophysics,
Icarus. Some funds (see Other costs in 3.1.6.2) are reserved for publications
of the results in Astrophysical Journal and Applied Optics.
A part of the data and codes will be included in the Database of Optical
Properties of small particles and will be freely accessible via the Internet.
An announcement of the database will be made in a scientific journal and on
different servers of the World Wide Web.
The approaches and software to be developed will have a wide field of
applications in astrophysics (to such objects as dust shells around stars of
different types, active galactic nuclei, etc.) as well as in other sciences
(atmospheric optics, biophysics, etc.) and industry (particle sizing, ecology
control measurements, etc.).
3.1.5 Description of Consortium
3.1.5.1 RESEARCH TEAMS
Participant 1 (P1)
==================
Prof. L.B.F.M. Waters - Astronomical Institute "Anton Pannekoek", University of
Amsterdam, NL and Institute for Astronomy, Catholic
University of Leuven, Leuven, BE
Dr. A. de Koter - Astronomical Institute "Anton Pannekoek", University of
Amsterdam, NL
F.J. Molster - Astronomical Institute "Anton Pannekoek", University of
Amsterdam, NL
J. Bouwman - Astronomical Institute "Anton Pannekoek", University of
Amsterdam, NL
C. Kemper - Astronomical Institute "Anton Pannekoek", University of
Amsterdam, NL
This team is formed by Prof. Waters (the head of the team and the co-ordinator
of the project) and his colleagues who specialize in ground and space
observations (in particular, those with the Infrared Space Observatory) of
various cosmic dusty objects and their interpretation. Some of their researches
have been made in a cooperation with the participants from Jena (P2) and
Petersburg (P3). Recent papers of the Amsterdam team members on the subject of
the project are as follows:
Task 3 (Electronic database)
In a joint work with colleagues from Jena, the absorption coefficients of
olivines and pyroxenes with different Mg/Fe ratios were measured by Jaeger,
Molster, Dorschner, Henning, Mutschke, and Waters ("Steps toward interstellar
silicate mineralogy. IV. The crystalline revolution." Astron. Astrophys.,
v. 339, 904, 1998). The data were included in the Database of Optical Constants
created by Henning, Il'in, Krivova, Michel, and Voshchinnikov ("WWW database of
optical constants for astronomy." Astron. Astrophys. Suppl., v. 136, 405, 1999).
Task 4 (Polarized radiation transfer)
Calculations of linear polarization due to single Thompson scattering in a disk
model were performed and analytical expressions for the relation between
polarization and infrared excess as a function of model parameters for edge-on
disks of classical Be stars were derived in the paper of Waters & Marlborough
("Constraints on Be star wind geometry by linear polarization and IR excess."
Astron. Astrophys., v. 256, 195, 1992).
A program for calculations of the emergent flux from a spherical shell
surrounding a single or binary star was developed in the University of Amsterdam
(see http://www.astro.uva.nl/~dekoter/).
Task 5 (Astrophysical applications)
The Monte Carlo method to treat the polarized radiative transfer in dust shells
was applied to young stars by Molster ("Modelling of circumstellar extinction
and polarization." Master's thesis, University of Amsterdam, 1995) and by
Voshchinnikov, Molster, and The ("Circumstellar extinction in the shells of
pre-main-sequence stars." Astron. Astrophys., v. 312, 243, 1996).
Several emission features at wavelengths between 20 and 45 micron were found
with the Short Wavelength Spectrometer (SWS) on board of the ISO in spectra of
the dust shells around evolved oxygen-rich stars by Waters, Molster et al.
("Mineralogy of oxygen-rich dust shells." Astron. Astrophys., v. 315, L361,
1996). The emission peaks were tentatively identified with crystalline forms of
silicates such as pyroxene and olivine.
The continuum-subtracted ISO SWS spectrum of the source AFGL 4106 was compared
with simple optically thin model spectra calculated for olivine and pyroxene
samples by Jaeger, Molster, Dorschner, Henning, Mutschke, and Waters
("Steps toward interstellar silicate mineralogy. IV. The crystalline
revolution." Astron. Astrophys., v. 339, 904, 1998).
ISO-SWS spectroscopy of the cool dusty envelopes surrounding two planetary
nebulae with [WC] central stars, BD+30 3639 and He 2-113 was discussed by
Waters, Beintema, Zijlstra, de Koter, Molster, Bouwman et al. ("Crystalline
silicates in planetary nebulae with [WC] central stars." Astron. Astrophys.,
v. 331, L61, 1998). It was found that the lambda < 15 micron region was
dominated by a rising continuum with prominent emission from C-rich dust
(Polycyclic Aromatic Hydrocarbons, PAHs), while the long wavelength part
showed narrow solid state features from crystalline silicates.
Infrared observations of the Red Rectangle were presented by Waters et al.
("An oxygen-rich dust disk surrounding an evolved star in the Red Rectangle."
Nature, v. 391, 868, 1998). They revealed the presence of oxygen-rich material:
prominent emission bands from crystalline silicates and absorption lines
arising from carbon dioxide. The oxygen-rich material is located in the
circumbinary disk.
ISO observations of gas and dust in the reflection nebula Ced 201 were analyzed
by Kemper et al. ("Far-infrared and submillimeter observations and physical
models of the reflection nebula Cederblad 201." Astrophys. J., v. 515, 649,
1999). The contribution of very small grains to the photoelectric heating rate
was estimated and used to constrain the total abundance of PAHs and small
grains.
SWS-ISO observations of the dusty circumstellar disk surrounding the isolated
young Fe star HD 142527 were discussed by Malfait, Waelkens, Bouwman, de Koter,
and Waters ("The ISO spectrum of the young star HD 142527." Astron. Astrophys.,
v. 345, 181, 1999). Two dust populations were discriminated: a warm component
which was dominated by very strong silicate emission at 10 micron and a cool
component, of which the spectrum was dominated by O-rich dust features. Besides
silicates, crystalline water-ice and hydrous silicates - which had been
detected in interplanetary dust particles - were found to be present in the
cold circumstellar environment as well.
There are many other recent researches of this team members on the project
subject. One can find their results for instance via the NASA Astronomical
Data System (ADS).
Participant 2 (P2)
==================
Prof. Th. Henning - Astrophysical Institute and University Observatory,
Friedrich Schiller University, Jena, DE
Dr. H. Mutschke - Astrophysical Institute and University Observatory,
Friedrich Schiller University, Jena, DE
Dr. G. Wurm - Astrophysical Institute and University Observatory,
Friedrich Schiller University, Jena, DE
S. Wolf - Tautenburg Observatory, Tautenburg; Astrophysical
Institute and University Observatory, Friedrich
Schiller University, Jena, DE
The head of this team, Prof. Henning, performed various studies in the fields
of light scattering and radiative transfer, laboratory experiments, observations
and modelling of different astrophysical objects. Drs. Mutschke and Wurm are
experts in laboratory astrophysics, and Mr. Wolf has done a large work with
radiative transfer codes. Different kinds of experiments (such as determination
of the optical constants of materials, simulations of grain growth in cosmic
conditions, etc.) have been made and new ones (including light scattering by
analogues of cosmic dust grains) have been recently started in the laboratory
of the Astrophysical Institute in Jena. The last researches of the Jena team
members on the subject of the project are as follows:
Task 1 (Light scattering theory)
The optical properties of spheroids were computed by several methods in the
paper of Henning & Stognienko ("Porous grains and polarization of light: the
silicate features." Astron. Astrophys., v. 280, 609, 1993).
The interaction of aggregate particles with radiation was modelled by
Stognienko, Henning & Ossenkopf ("Optical properties of coagulated particles."
Astron. Astrophys., v. 296, 797, 1995) and Henning & Stognienko ("Dust
opacities for protoplanetary accretion disks - influence of dust aggregates."
Astron. Astrophys., v. 311, 291, 1996). They also discussed the applicability
of different Effective Medium Theories for such particles.
A new statistical approach to calculate the optical properties of aggregates was
suggested by Michel, Henning, Stognienko, and Rouleau ("Extinction properties
of dust grains: a new computational technique." Astrophys. J., v. 468, 834,
1996). This method allows one to find the properties for an ensemble of randomly
oriented aggregates and is in particular efficient for highly absorbing
materials.
Task 2 (Light scattering experiments)
New light scattering experiments on aggregate particles started in the Jena
laboratory recently, are in the line of the experimental investigations of grain
growth by coagulation in cosmic conditions (Blum, Wurm, and Poppe, "The CODAG
sounding rocket experiment to study aggregation of thermally diffusing dust
particles." Adv. Space Res., v. 23, 1267, 1999; Wurm & Blum, "Experiments on
preplanetary dust aggregation." Icarus, v. 132, 125, 1998; Blum, Wurm, Kempf,
and Henning, "The Brownian motion of dust particles in the Solar nebula - an
experimental approach to the problem of pre-planetary dust aggregation."
Icarus, v. 124, 441, 1996).
A large series of works presents the optical constants of numerous materials of
astronomical interest measured in the laboratory of the Astrophysical Institute
in Jena in a wide spectral region by means of analysis of transmitted and
scattered radiation (see, e.g., the papers published during the last year -
Mutschke, Andersen, Clement, Henning, and Peiter, "Infrared properties of SiC
particles." Astron. Astrophys., v. 345, 187, 1999; Andersen, Jaeger, Mutschke,
Braatz, Clement, Henning, Joergensen, and Ott, "Infrared spectra of meteoritic
SiC grains." Astron. Astrophys., v. 343, 933, 1999; Schnaiter, Henning,
Mutschke, Kohn, Ehbrecht, and Huisken, "Infrared spectroscopy of nano-sized
carbon grains produced by laser pyrolysis of acetylene - Analogue materials for
interstellar grains." Astrophys. J., v. 519, 687, 1999; Michel, Henning, Jaeger,
and Kreibig, "Optical extinction by spherical carbonaceous particles." Carbon,
v. 37, 391, 1999 and references therein).
Task 3 (Electronic database)
Numerous laboratory experiments in Jena on determination of optical constants
of various materials (silicates, oxides, sulfides, carbides, carbonaceous
species, etc. - see Henning, Il'in, Krivova, Michel, and Voshchinnikov, "WWW
database of optical constants for astronomy." Astron. Astrophys. Suppl., v. 136,
405, 1999 for a review) have resulted in the creation of the Database of Optical
Constants which has a free access via the Internet (http://www.astro.uni-jena.de
/Users/database/entry.html).
Task 4 (Polarized radiation transfer)
A number of radiative transfer codes have been developed in the Jena group:
a 1D code (Thamm, Steinacker, and Henning, "Ambiguities of parameterized dust
disk models for young stellar objects." Astron. Astrophys., v. 287, 493, 1994);
2D codes (Men'shchikov & Henning, "Radiation transfer in circumstellar disks."
Astron. Astrophys., v. 318, 879, 1997; Manske & Henning, "Two-dimensional
radiative transfer with transiently heated particles: methods and applications."
Astron. Astrophys., v. 337, 85, 1998) and a 3D code (Steinacker & Henning, "3D
continuum radiative transfer". in: H.U. Kaeufl, R. Siebenmorgen (eds.), The Role
of Dust in the Formation of Stars, Springer, 355, 1996).
A computer code to simulate the polarized radiation transfer in media of
arbitrary geometry using Monte Carlo simulations was developed by Fischer,
Henning, and Yorke ("Simulation of polarization maps. I. Protostellar
envelopes." Astron. Astrophys., v. 284, 187, 1994; "Simulation of polarization
maps. II. The circumstellar environment of pre-main sequence objects." Astron.
Astrophys., v. 308, 863, 1996) and extended by Wolf, Fischer, and Pfau
("Radiative transfer in the clumpy environment of young stellar objects."
Astron. Astrophys., v. 340, 103, 1998).
Task 5 (Astrophysical applications)
The radiation transfer codes developed in Jena have been applied to different
cosmic objects, for instance: AGN by Wolf & Henning ("AGN polarization models."
Astron. Astrophys., v. 341, 675, 1999); HL Tau by Men'shchikov, Henning, and
Fischer ("Self-consistent model of the dusty torus around HL Tauri." Astrophys.
J., v. 519, 257, 1999); Chamaeleon region by Ageorges, Fischer, Stecklum,
Eckart, and Henning ("The Chamaeleon infrared nebula: a polarization study with
high angular resolution." Astrophys. J., v. 463, L101, 1996).
Interstellar extinction and polarization in the infrared bands at 10 and 20
microns were modelled by Henning & Stognienko ("Porous grains and polarization
of light: the silicate features." Astron. Astrophys., v. 280, 609, 1993). The
UV bump in the interstellar extinction curves was considered by Rouleau,
Henning, and Stognienko ("Constraints on the properties of the 2175 A
interstellar feature carrier." Astron. Astrophys., v. 322, 633, 1997) and
Schnaiter, Mutschke, Henning, Lindackers, Stecker, and Roth ("Ultraviolet
spectroscopy of matrix-isolated amorphous carbon particles." Astrophys. J.,
v. 464, L187, 1996).
Many other astrophysical researches were performed in Jena. Some references can
be found in the reviews of Dorschner & Henning ("Dust metamorphosis in the
Galaxy." Astron. Astrophys. Review, v. 6, 271, 1995), Henning ("Interstellar dust
grains - an overview." IAU Symp. N 178, 343, 1996), Henning ("Laboratory
astrophysics of circumstellar dust." IAU Symp. N 191, 1998), Henning & Salama
("Carbon in the Universe." Science, v. 282, 2204, 1998), Henning ("Chemistry
and physics of nano- and microparticles." Chemical Society Review, v. 27, 315,
1998).
Participant 3 (P3)
==================
Prof. N.V. Voshchinnikov - Astronomy Department and Sobolev Astronomical
Institute, St. Petersburg University, RU
Dr. V.B. Il'in - Sobolev Astronomical Institute, St. Petersburg
University, RU
M.S. Prokop'eva - 24 years old; Astronomy Department, St. Petersburg
University, RU
D.A. Semenov - 22 years old; Astronomy Department, St. Petersburg
University, RU
The head of the team, Prof. Voshchinnikov, has undertook a number of researches
on light scattering theory, radiative transfer, and their astrophysical
applications. Many of these works were made together with Dr. Il'in and other
colleagues. Recent investigations of the members of this team on the subject of
the project are as follows:
Task 1 (Light scattering theory)
A new approach to solution of the light scattering problem for homogeneous
and coated confocal spheroids in the frame of the Separation of variables method
has been suggested by Farafonov and then developed by Voshchinnikov & Farafonov
("Optical properties of spheroidal particles." Astrophys. Space Science,
v. 204, 19, 1993), Farafonov, Voshchinnikov, and Somsikov ("Light scattering by
a core-mantle spheroidal particle." Appl. Opt., v. 35, 5412, 1996),
Voshchinnikov ("Electromagnetic scattering by homogeneous and coated spheroids:
calculations using the separation of variables method." J. Quant. Spectrosc.
Rad. Transfer, v. 55, 627, 1996).
First steps to the realization of a new solution to the light scattering problem
based on the T-matrix method were made by Farafonov, Il'in, and Henning ("A new
solution of the light scattering problem for axisymmetric particles." J. Quant.
Spectrosc. Rad. Transfer, v. 63, 205, 1999).
The applicability of the Rayleigh and quasistatic approximations for spheroidal
particles was considered by Somsikov & Voshchinnikov ("On the applicability of
the Rayleigh approximation for coated spheroids in the near-infrared." Astron.
Astrophys., v. 345, 315, 1999) and Voshchinnikov & Farafonov ("On applicability
of quasistatic and Rayleigh approximations for spheroidal particles." Opt.
Spectrosc., 1999, in press).
A numerical code for multi-layered spheres and a new "layered-sphere" EMT were
developed by Voshchinnikov & Mathis ("Calculating cross sections of composite
interstellar grains." Astrophys. J., 1999, v. 526, N1 - the LANL-preprint
astro-ph/9908240).
Task 3 (Electronic database)
A database of optical constants for astronomy was created in a joint work with
colleagues from Jena (Henning, Il'in, Krivova, Michel, and Voshchinnikov "WWW
database of optical constants for astronomy." Astron. Astrophys. Suppl., v. 136,
405, 1999). It has a free access via the Internet: http://www.astro.spbu.ru/
JPDOC/entry.html.
A comparison of different computational methods and some benchmark results were
presented by Hovenier, Lumme, Mishchenko, Voshchinnikov et al. ("Computations
of scattering matrices of four types of non-spherical particles using diverse
methods." J. Quant. Spectrosc. Rad. Transfer, v. 55, 695, 1996) and by
Voshchinnikov, Il'in, Henning et al. ("Extinction and polarization of radiation
by absorbing spheroids: shape/size effects and some benchmarks." J. Quant.
Spectrosc. Rad. Transfer, 1999, in press - the LANL-preprint astro-ph/9908241).
Task 4 (Polarized radiation transfer)
A new version of the Monte Carlo method (the method of symmetrized trajectories)
for polarized radiation transfer calculations in axisymmetric dust shells was
developed by Voshchinnikov & Karjukin ("Multiple scattering of polarized
radiation in circumstellar dust shells." Astron. Astrophys., v. 288, 883, 1994).
Task 5 (Astrophysical applications)
An application of the model of homogeneous spheroids to the interstellar
extinction and polarization was done by Voshchinnikov & Farafonov ("Optical
properties of spheroidal particles." Astrophys. Space Science, v. 204, 19,
1993). A first step to the development of a new model of composite interstellar
grains was made by Voshchinnikov & Mathis ("Calculating cross sections of composite interstellar
grains." Astrophys. J., 1999, v. 526, N1, in press - the LANL-preprint
astro-ph/9908240).
The particle shape effects on the temperature of interstellar grains were
estimated by Voshchinnikov, Semenov, and Henning ("The temperature of
non-spherical interstellar grains." Astron. Astrophys., 1999, in press - the
LANL-preprint astro-ph/9908235).
Applications of Monte Carlo simulations to the calculation of the circumstellar
extinction and polarization curves were made by Voshchinnikov, Molster, and The
("Circumstellar extinction in the shells of pre-main-sequence stars." Astron.
Astrophys., v. 312, 243, 1996) and Voshchinnikov et al. ("Monte Carlo simulation
of light scattering in the envelopes of young stars." Astron. Astrophys.,
v. 294, 547, 1995; "Dust shells around Herbig Ae/Be stars." Astron. Reports.
v. 42, 46, 1998).
Polarimetric maps and infrared fluxes of young stars were modelled using Monte
Carlo simulations of polarized radiation transfer by Krivova, Il'in et al.
("Dust around Herbig Ae stars: additional constraints from their photometric and
polarimetric variability." in: M.E. Kress, A.G.G.M. Tielens, and Y.J. Pendleton
(eds.), From Stardust to Planetesimals: Contributed Papers, NASA-CP #3343, 37,
1997; "Dust shells around Herbig Ae/Be stars with Algol-like minima: modelling
of photometric observations." Astron. Letters, v. 23, 791, 1997; "Dust grains
around Herbig Ae/Be stars: porous, cometary-like grains?." Icarus, 1999, in
press).
The motion of non-spherical dust grains in the shells of evolved stars due to
radiation pressure was considered by Il'in & Voshchinnikov ("Radiation pressure
on non-spherical dust grains in envelopes of late-type giants." Astron.
Astrophys. Suppl., v. 128, 187, 1998).
Participant 4 (P4)
==================
Dr. V.A. Babenko - Stepanov Institute of Physics, Belarus Academy of
Science, Minsk, BY
Dr. L.G. Astafieva - Stepanov Institute of Physics, Belarus Academy of
Science, Minsk, BY
Dr. A.A. Kokhanovsky - Stepanov Institute of Physics, Belarus Academy of
Science, Minsk, BY
Dr. A.F. Sinyuk - 35 years old; Stepanov Institute of Physics, Belarus
Academy of Science, Minsk, BY
P.K. Petrov - 26 years old; Stepanov Institute of Physics, Belarus
Academy of Science, Minsk, BY
This team includes the scientists from the Stepanov Institute of Physics which
was a leading center of studies of light scattering and its various applications
in the former Soviet Union. Dr. Babenko performed many different researches in
the field of light scattering by spherical and non-spherical particles. Dr.
Astafieva is an expert in thermophysics and optics. Dr. Kokhanovsky is a
well-known specialist in approximate methods of light scattering. Dr. Sinyuk
has solved several inverse tasks in atmosphere optics. The recent works of these
scientists on the subject of the project are as follows:
Task 1 (Light scattering theory)
A detailed study of the optical properties of inhomogeneous and anisotropic
spherical particles was done in the book of Prishivalko, Babenko, and Kuz'min
("Scattering and absorption of light by inhomogeneous and anisotropic spherical
particles." Nauka i Tekhnika, Minsk, 1984).
A description of various approximate methods in light scattering by spherical
and non-spherical particles was presented in the book of Kokhanovsky ("Optics
of Light Scattering Media". Wiley, Chichester, 1999).
The variational boundary condition method was developed by Petrov & Babenko
("The variational boundary condition method for solving problems of light
scattering by nonspherical particles." J. Quant. Spectrosc. Rad. Transfer,
v. 63, 237, 1999) to solve the problem of light scattering by non-spherical
particles. An improved algorithm for T-matrix computations of electromagnetic
radiation scattering by spheroidal objects based on the expansions of the Bessel
and Legendre functions in finite series was suggested by Babenko ("Improved
algorithm for T-matrix computation of EM scattering by spheroidal objects." in:
Light scattering by nonspherical particles: theory, measurements, and
application (ed. M.I. Mishchenko, L. Travis and J.W. Hovenier), N.Y., 1998,
p.159).
The size effect in metallic nanoparticles was studied in the paper of Oshchepkov
& Sinyuk ("Optical sizing of ultrafine metallic particles: retrieval of
particle size distribution from spectral extinction measurements." J. Colloid
Interface Science, v. 208, 137, 1998).
The internal thermal fields in non-rotating spheroidal particles illuminated by
intense laser pulse were considered by Astafieva & Babenko ("Heating of a
spheroidal particle by intense laser radiation." J. Quant. Spectrosc. Rad.
Transfer, v. 63, 459, 1999). It was found that the heating of particles was very
inhomogeneous and the difference in temperatures could reach several hundred
kelvin.
Task 3 (Electronic database)
Dr. Babenko has created a database (under FoxPro/DOS) that contains about 8000
references to the papers devoted to the problem of light scattering by small
particles.
There exists a large number of light scattering codes developed by different
persons in the Stepanov Institute of Physics. These codes can treat both single
size particles (such as homogeneous and layered spheres, infinite cylinders,
spheroids, spheres with variable refractive index, etc.) and polydisperse
ensembles.
Task 5 (Astrophysical applications)
The inverse problem of determination of refractive index and size/shape
distributions from atmospheric experiments has been solved for non-spherical
particles by Oshchepkov, Isaka, Gayer, Sinyuk et al. ("Microphysical properties
of mixed phase and ice clouds retrieved from in situ airborne measurements."
Geophys. Research Letters, 1999, in press.).
Heating and destruction of particles (including terrestrial aerosol particles)
were considered in a number of papers by Prishivalko, Astafieva, and Leiko
("Heating and destruction of particles exposed to intense laser radiation."
Appl. Opt., v. 35, 965, 1996), Astafieva, Prishivalko, and Leiko ("Disruption
of hollow aluminum particles by intense laser radiation." J. Opt. Soc. Amer.,
v. B14, 432, 1997), Astafieva & Prishivalko ("Heating of solid aerosol
particles exposed to intense optical radiation." Int. J. Heat Mass Transfer,
v. 4, 489, 1998), Prishivalko, Babenko et al. ("On thermal destruction of
atmospheric ice grains by radiation with lambda=10.6 micron." Atmosph. Ocean
Optics, v. 11, 1, 1998), Astafieva & Babenko ("Heating of a spheroidal
particle by intense laser radiation." J. Quant. Spectrosc. Rad. Transfer, v. 63,
459, 1999). The approach developed will be used in consideration of heating and
crystallization of circumstellar dust grains.
Participant 5 (P5)
==================
Dr. V.P. Tishkovets - Astronomical Observatory, Kharkov University, UA
Dr. N.N. Kiselev - Astronomical Observatory, Kharkov University, UA
P.V. Litvinov - 26 years old; Astronomical Observatory, Kharkov
University, UA
S.A. Beletsky - 28 years old; Astronomical Observatory, Kharkov
University, UA
The head of the team, Dr. Tishkovets, and Mr. Litvinov made many investigations
of light scattering by clusters of particles - analogues of interplanetary dust
grains. Dr. Kiselev is a high-level expert in polarimetry and world known
observer of comets, asteroids, and stars. Mr. Beletsky is one of the authors of
the IRIS - a special astronomical information system. The recent works of the
team members on the subject of the project are as follows:
Task 1 (Light scattering theory)
Asymptotic formulas for the extinction and absorption cross sections for
randomly oriented multiple-sphere clusters were obtained by Tishkovets &
Litvinov ("Coefficient of light extinction by randomly oriented clusters of
spherical particles in the double scattering approximation." Opt. Spectrosc.,
v. 81, 319, 1996) and Litvinov & Tishkovets ("Light absorption coefficients for
randomly oriented clusters of spherical particles in the double-scattering
approximation." Opt. Spectrosc., v. 86, 87, 1999).
A new mechanism of coherent effects in backscattering by closely packed
particles was discovered and discussed in detail by Tishkovets, Shkuratov, and
Litvinov ("Comparison of collective effects at scattering by randomly oriented
clusters of spherical particles." J. Quant. Spectrosc. Rad. Transfer, v. 61,
767, 1999). It was shown that in the case of randomly oriented clusters the
enhancement backscattering of light and negative linear polarization occurred
at nearly zero phase angles. Both phenomena are typical of interplanetary
and cometary dust.
Task 2 (Light scattering experiments)
Properties of the negative polarization of light scattered by different samples
at small phase angles were studied experimentally and a comparative analysis of
different theoretical models of this phenomenon was made by Shkuratov,
Muinonen, Tishkovets et al. ("A critical review of theoretical models for the
negative polarization of light scattered by atmosphereless Solar system bodies."
Earth, Moon & Planets, v. 6, 201, 1994).
Task 3 (Electronic database)
An universal information system IRIS was developed in the Astronomical
Observatory of the Kharkov University (all documentation on the system is freely
accessible via the Internet - http://members.xoom.com/cyteg). The system
includes the IRIS-integrator, WisA-subsystem and editor Head-Edit. The
IRIS-integrator creates, sorts, filters and makes processing of graphic data
files by making use of a special computer language Bastis. The WisA-subsystem
serves for visualization and analysis of the data. The editor Head-Edit allows
users to edit information connected with data and convert all files into FITS
and other formats. All components of the IRIS are supplied by user-friendly
Windows-like graphic interfaces with rich service functions.
The experience gained during the work on the IRIS system will be used in the
development of the Database of Optical Properties and in particular its
library of the optical properties (see above 3.1.4.1).
Task 4 (Polarized radiation transfer)
A model of collective effects in light polarization by systems of randomly
oriented clusters of spherical particles has been proposed. In this model the
interference of scattered waves by different scatterers is taken into account
(Tishkovets & Litvinov, "Electromagnetic scattering by a system of chaotically
oriented clusters of spherical particles." Radiophys. Electronics, v. 3, 57,
1998).
Task 5 (Astrophysical applications)
Observations of a number of dusty comets in a wide range of the phase angles and
wavelengths were fulfilled and processed by Kiselev and his co-workers
(Chernova, Jockers, and Kiselev "Imaging photometry and color of comet
Shoemaker-Levy 9." Icarus, v. 121, 38, 1996; Kolokolova, Jockers, Chernova, and
Kiselev "Properties of cometary dust from color and polarization." Icarus,
v. 126, 351, 1997; Kiselev & Velichko "Polarimetry and photometry of comet
C/1996 B2 Hyakutake." Icarus, v. 133, 286, 1998; Kiselev "Some problems of
cometary polarimetry: a review." Astron. Vestn., v. 33, 181, 1999).
The properties of cometary dust were studied using the inverse problem solution
by Kolokolova, Jockers, Chernova, and Kiselev ("Properties of cometary dust
from color and polarization." Icarus, v. 126, 351, 1997).
The oppositional effects in brightness and polarization observed for cometary
and interplanetary dust have been discussed by Tishkovets & Litvinov
("Opposition effects in scattering of light by regolith-like media." Astron.
Vestn., v. 33, 186, 1999). They found that the properties of the fields near
scatterers played an important role in originating the effects.
Participant 6 (P6)
==================
Prof. A.Ya. Perel'man - St. Petersburg State Forest Technical Academy, RU
Dr. T.V. Wielgorskaya - Komarov's Botanical Institute, Russian Academy of
Sciences, St. Petersburg, RU and St. Petersburg State
Forest Technical Academy, RU
T.V. Zinov'eva - 23 years old; Astronomy Department, St. Petersburg
University, RU
Prof. Perel'man is a world-known expert in the light scattering theory and his
participation in the project is essential. Dr. Wielgorskaya is the author of
a widely used database in botany. The recent works of the team on the subject
of the project are as follows:
Task 1 (Light scattering theory)
An important approximation for optically soft particles (S-approximation or
Perel'man approximation) was developed in the paper of Perel'man ("Extinction
and scattering by soft particles." Appl. Opt., v. 30, 475, 1991). From this
approximation, other approximations like the Rayleigh, Rayleigh-Gans,
van de Hulst (anomalous diffraction) ones can be obtained.
The problem of light scattering by a spherical particle whose refractive index
arbitrarily depends on the distance from the particle center was solved by
Perel'man ("Scattering by particles with radially variable refractive index."
Appl. Opt., v. 35, 5452, 1996).
The method of conservation of the azimuthal structure of a perturbation in the
problems of diffraction by spherically symmetric scatterers (a phi-method)
was developed for an exact solution of the Mie problem and its generalizations
in the papers of Perel'man ("Integral presentation of field vectors in the
problem of diffraction by a sphere: I. General form of permissible waves in the
Mie problem." Opt. Spectrosc., v. 86, 105, 1999; "II. Phi-method of
solution of the boundary problem for Mie diffraction." Opt. Spectrosc., v. 86,
272, 1999).
The small angles S-approximations for the Stokes parameters were constructed by
Perel'man ("S-approximation for the Mie small angles amplitudes", Appl. Opt.,
1999, submitted). This approach allows the Hulst and Fraunhofer theories to be
developed, simultaneously. In particular, the new expression for the scattering
function can be treated both within the framework of the theory of anomalous
diffraction (generalization of the Hulst formulas for efficiencies) and the
Kirchhoff approximation. The latter is insensitive to the optical properties of
material while the expression obtained does take into account the dependence of
the scattering function on the refractive index of substance. This fact is of
particular importance in the astrophysical applications.
Task 3 (Electronic database)
The database of generic names of seed plants for botanic purposes was created
by Wielgorskaya ("Dictionary of generic names of seed plants." Columbia
University Press, New York, 1995). Later an electronic shell for this database
was made. The experience gained during this work will be used in the planned
development of the Database of Optical Properties.
Task 5 (Astrophysical applications)
The results obtained by Shifrin, Perel'man and Kokorin ("Optical properties of
particles of the complicated structure." J. Techn. Physics Lett., v. 11, 790,
1985; "Light scattering by two layers dielectric particles with continuous
optical properties." Opt. Spectrosc., v. 59, 597, 1985) allow one to essentially
improve the conventional scattering function of antireflection by large fluffy
particles of the interplanetary dust.
The complementary nature of the research teams is seen from the following table:
================================================================================
| Team | Main scientific interests |
|--------------------|---------------------------------------------------------|
| P1 (Amsterdam) | observations of interstellar and circumstellar dust and |
| | interpretation of the data |
| | |
| P2 (Jena) | laboratory astrophysics; astrophysical applications of |
| | radiative transfer; multi-wavelength observations |
| | |
| P3 (St. Petersburg)| light scattering and radiative transfer and their |
| | astrophysical applications |
| | |
| P4 (Minsk) | light scattering and its applications to atmospheric |
| | optics, biophysics, industry |
| | |
| P5 (Kharkov) | theory and experiments on light scattering; observations|
| | of interplanetary dust and interpretation of the data |
| | |
| P6 (St. Petersburg)| general theory of light scattering; databases |
================================================================================
3.1.5.2 SCIENTIFIC REFERENCES
P1 team:
1.1. Waters L.B.F.M., Marlborough J.M. (1992)
Constraints on Be star wind geometry by linear polarization and IR excess.
Astronomy & Astrophysics, v. 256, 195-204.
1.2. Waters L.B.F.M., Molster F.J., et al. (1996)
Mineralogy of oxygen-rich dust shells.
Astronomy & Astrophysics, v. 315, L361-L364.
1.3. Waters L.B.F.M., Waelkens C. (1998)
Herbig Ae/Be stars.
Annual Review of Astronomy & Astrophysics, v. 36, 233-266.
1.4. Waters L.B.F.M., Waelkens C., van Winckel H., Molster F.J.,
Tielens A.G.G.M., van Loon J.Th., Morris P.W., Cami J., Bouwman J,
de Koter A., et al. (1998)
An oxygen-rich dust disk surrounding an evolved star in the Red Rectangle.
Nature, v. 391, 868-871.
1.5. Waters L.B.F.M., Beintema D.A., Zijlstra A.A., de Koter A., Molster F.J.,
Bouwman J., et al. (1998)
Crystalline silicates in planetary nebulae with [WC] central stars.
Astronomy & Astrophysics, v. 331, L61-L64.
1.6. Jaeger C., Molster F.J., Dorschner J., Henning Th., Mutschke H.,
Waters L.B.F.M. (1998)
Steps toward interstellar silicate mineralogy. IV. The crystalline
revolution.
Astronomy & Astrophysics, v. 339, 904-916.
1.7. Waters L.B.F.M., Molster F.J., Waelkens C. (1999)
Crystalline silicates in circumstellar shells,
in: Solid interstellar matter: the ISO Revolution (eds. L. d'Hendecourt,
C. Joblin, A. Jones), Springer, pp. 219-229.
1.8. Kemper C., et al. (1999)
Far-infrared and submillimeter observations and physical models of the
reflection nebula Cederblad 201.
Astrophysical Journal, v. 515, 649-656.
1.9. Malfait K., Waelkens C., Bouwman J., de Koter A., Waters L.B.F.M. (1999)
The ISO spectrum of the young star HD 142527.
Astronomy & Astrophysics, v. 345, 181-186.
1.10.Lamers H.J.G.L.M., Haser S., de Koter A., et al. (1999)
The ionization in the winds of O stars and the determination of mass-loss
rates from ultraviolet lines.
Astrophysical Journal, v. 516, 872-886.
P2 team:
2.1. Henning Th., Stognienko R. (1993)
Porous grains and polarization of light: the silicate features.
Astronomy & Astrophysics, v. 280, 609-615.
2.2. Fischer O., Henning Th., Yorke H.W. (1994)
Simulation of polarization maps. I. Protostellar envelopes.
Astronomy & Astrophysics, v. 284, 187-209.
2.3. Stognienko R., Henning Th., Ossenkopf V. (1994)
Optical properties of coagulated particles.
Astronomy & Astrophysics, v. 296, 797-807.
2.4. Dorschner J., Henning Th. (1995)
Dust metamorphosis in the Galaxy.
Astronomy & Astrophysics Review, v. 6, 271-341.
2.5. Michel B., Henning Th., Stognienko R., Rouleau F. (1996)
Extinction properties of dust grains: a new computational technique.
Astrophysical Journal, v. 468, 834-841.
2.6. Schnaiter M., Mutschke H., Henning Th. et al. (1996)
Ultraviolet spectroscopy of matrix isolated amorphous carbon particles.
Astrophysical Journal, v. 464, L187-L190.
2.7. Men'shchikov A.V., Henning Th. (1997)
Radiation transfer in circumstellar disks.
Astronomy & Astrophysics, v. 318, 879-907.
2.8. Rouleau F., Henning Th., Stognienko R. (1997)
Constraints on the properties of the 2175 interstellar feature carrier.
Astronomy & Astrophysics, v. 322, 633-645.
2.9. Wolf S., Fischer O., Pfau W. (1998)
Radiative transfer in the clumpy environment of young stellar objects.
Astronomy & Astrophysics, v. 340, 103-116.
2.10.Henning Th. (1998)
Chemistry and physics of cosmic nano- and microparticles.
Chemical Society Reviews, v. 27, 315-321.
P3 team:
3.1. Voshchinnikov N.V., Farafonov V.G. (1993)
Optical properties of spheroidal particles.
Astrophysics & Space Science, v. 204, 19-86.
3.2. Voshchinnikov N.V., Karjukin V.V. (1994)
Multiple scattering of polarized radiation in circumstellar dust shells.
Astronomy & Astrophysics, v. 288, 883-896.
3.3. Voshchinnikov N.V., Molster F.J., The P.S. (1996)
Circumstellar extinction in the shells of pre-main-sequence stars.
Astronomy & Astrophysics, v. 312, 243-255.
3.4. Farafonov V.G., Voshchinnikov N.V., Somsikov V.V. (1996)
Light scattering by a core-mantle spheroidal particle.
Applied Optics, v. 35, 5412-5426.
3.5. Voshchinnikov N.V. (1996)
Electromagnetic scattering by homogeneous and coated spheroids:
calculations using the separation of variables method.
Journal of Quantitative Spectroscopy & Radiative Transfer, v. 55, 627-636.
3.6. Hovenier J.W., Lumme K., Mishchenko M.I., Voshchinnikov N.V. et al. (1996)
Computations of scattering matrices of four types of non-spherical
particles using diverse methods.
Journal of Quantitative Spectroscopy & Radiative Transfer, v. 55, 695-705.
3.7. Il'in V.B., Voshchinnikov N.V. (1998)
Radiation pressure on non-spherical dust grains in envelopes of late-type
giants.
Astronomy & Astrophysics Supplement, v. 128, 187-196.
3.8. Somsikov V.V., Voshchinnikov N.V. (1999)
On the applicability of the Rayleigh approximation for coated spheroids in
the near-infrared.
Astronomy & Astrophysics, v. 345, 315-320.
3.9. Henning Th., Il'in V.B., Krivova N.A., Michel B., Voshchinnikov N.V. (1999)
WWW database of optical constants for astronomy.
Astronomy & Astrophysics Supplement, v. 136, 405-406.
3.10.Farafonov V.G., Il'in V.B., Henning Th. (1999)
A new solution of the light scattering problem for axisymmetric particles.
Journal of Quantitative Spectroscopy & Radiative Transfer, v. 63, 205-215.
P4 team:
4.1. Prishivalko A.P., Babenko V.A., Kuz'min V.N. (1984)
Scattering and absorption of light by inhomogeneous and anisotropic
spherical particles.
Nauka i Tekhnika, Minsk, 264 pp.
4.2. Prishivalko A.P., Astafieva L.G., Leiko S.T. (1996)
Heating and destruction of particles exposed to intense laser radiation.
Applied Optics, v. 35, 965-972.
4.3. Astafieva L.G., Prishivalko A.P., Leiko S.T. (1997)
Disruption of hollow aluminum particles by intense laser radiation.
Journal of Optical Society of America, v. 14, 432-436.
4.4. Astafieva L.G., Ledneva G.P. (1997)
Thermal effect of pumping intensity on active medium of neodymium-glass
microlaser.
Applied Optics, v. 36, 9360-9370.
4.5. Kokhanovsky A.A., Macke A. (1997)
Integral light scattering and absorption characteristics of large
non-spherical particles.
Applied Optics, v. 36, 8785-8790.
4.6. Oshchepkov S.L., Sinyuk A.F. (1998)
Optical sizing of ultrafine metallic particles: retrieval of particle
size distribution from spectral extinction measurements.
Journal of Colloidal & Interface Science, v. 208, 137-146.
4.7. Kokhanovsky A.A., Babenko V.A., Barun V.V. (1998)
On asymptotic values of light fluxes scattered by large spherical
particles between two angles.
J. Phys. D: Appl. Phys., v. 31, 1817-1822.
4.8. Kokhanovsky A.A. (1999)
Optics of Light Scattering Media.
J. Wiley, Chichester, 217 pp.
4.9. Petrov P.K., Babenko V.A. (1999)
The variational boundary condition method for solving problems of light
scattering by nonspherical particles.
Journal of Quantitative Spectroscopy & Radiative Transfer, v. 63, 237-250.
4.10.Astafieva L.G., Babenko V.A. (1999)
Heating of a spheroidal particle by intense laser radiation.
Journal of Quantitative Spectroscopy & Radiative Transfer, v. 63, 459-468.
P5 team:
5.1. Shkuratov Yu.G., Muinonen K., ..., Tishkovets V.P. et al. (1994)
A critical review of theoretical models for the negative polarization of
light scattered by atmosphereless Solar system bodies.
Earth, Moon & Planets, v. 6, 201-246.
5.2. Tishkovets V.P., Litvinov P.V. (1996)
Coefficient of light extinction by randomly oriented clusters of spherical
particles in the double scattering approximation.
Optics & Spectroscopy, v. 81, 319-322.
5.3. Chernova G., Jockers K., Kiselev N. (1996)
Imaging photometry and color of comet Shoemaker-Levy 9.
Icarus, v. 121, 38-45.
5.4. Kolokolova L., Jockers K., Chernova G., Kiselev N. (1997)
Properties of cometary dust from color and polarization.
Icarus, v. 126, 351-361.
5.5. Tishkovets V.P., Litvinov P.V. (1998)
Electromagnetic scattering by a system of chaotically oriented clusters of
spherical particles.
Radiophysics & Electronics, v. 3, 57-61.
5.6. Kiselev N.N., Velichko F.P. (1998)
Polarimetry and photometry of comet C/1996 B2 Hyakutake.
Icarus, v. 133, 286-292.
5.7. Kiselev N.N. (1999)
Some problems of cometary polarimetry: a review.
Astronomicheskii Vestnik, v. 33, 181-185.
5.8. Tishkovets V.P., Litvinov P.V. (1999)
Opposition effects in scattering of light by regolith-like media.
Astronomicheskii Vestnik, v. 33, 186-192.
5.9. Litvinov P.V., Tishkovets V.P. (1999)
Light absorption coefficients for randomly oriented clusters of spherical
particles in the double-scattering approximation.
Optics & Spectroscopy, v. 86, 87-90.
5.10.Tishkovets V.P., Shkuratov Yu.G., Litvinov P.V. (1999)
Comparison of collective effects at scattering by randomly oriented
clusters of spherical particles.
Journal of Quantitative Spectroscopy & Radiative Transfer, v. 61, 767-773.
P6 team:
6.1. Shifrin K.S., Perel'man A.Ya., Kokorin A.M. (1985)
Optical properties of particles of the complicated structure.
Journal of Technical Physics Letters, v. 11, 790-794.
6.2. Shifrin K.S., Perel'man A.Ya., Kokorin A.M. (1985)
Light scattering by two layers dielectric particles with continuous optical
properties.
Optics & Spectroscopy, v. 59, 597-602.
6.3. Perel'man A.Ya. (1991)
Extinction and scattering by soft particles.
Applied Optics, v. 30, 475-484.
6.4. Perel'man A.Ya. (1994)
Improvement of the convergence of series for absorbing cross-section of a
soft sphere.
Optics & Spectroscopy, v. 77, 643-647.
6.5. Perel'man A.Ya. (1995)
Diffraction by spherically symmetric inhomogeneous scatterers.
Optics & Spectroscopy, v. 78, 741-750.
6.6. Wielgorskaya T.V. (1995)
Dictionary of generic names of seed plants.
Columbia University Press, New York, 570 pp.
6.7. Perel'man A.Ya. (1996)
Scattering by particles with radially variable refractive index.
Applied Optics, v. 35, 5452-5460.
6.8. Perel'man A.Ya. (1999)
Integral presentation of field vectors in the problem of diffraction by a
sphere: I. General form of permissible waves in the Mie problem.
Optics & Spectroscopy, v. 86, 105-114.
6.9. Perel'man A.Ya. (1999)
Integral presentation of field vectors in the problem of diffraction by a
sphere: II. Phi-method of solution of the boundary problem for Mie
diffraction.
Optics & Spectroscopy, v. 86, 272-287.
3.1.6. Management
For each of the five tasks to be done, there is a coordinating participant (see
3.1.4.1) and it is planned that each 3-6 months other participants involved in
the work on the task will send a technical report to that participant as well as
to the co-ordinator of the project.
The cooperative work will be based on information exchange via e-mail, fax, mail
and phone, and in particular during the planned exchange visits of scientists.
The ready results in the form of preprints, technical documentation, codes, etc.
will be distributed among the consortium teams via e-mail and the Internet.
In the middle of the work on the project, a co-ordination meeting of some
participants is planned to be hold in St. Petersburg or Minsk.
Such a scheme of management of a cooperative work and exchange of results has
been successfully used during the work on a two-year joint project of the
Astrophysical Institute and University Observatory of the Friedrich Schiller
University, Jena (P2), the Astronomical Institute of the Petersburg University
(P3) and two other institutes from Russia. That project was supported by the
Volkswagen Foundation (Germany) in 1997-1999 and involved about 15 scientists.
3.1.6.1. PLANNING & TASKS ALLOCATION
======================================================================
| Tasks | Participants | Months |
| | | 1-6 | 7-12 | 13-18| 19-24| 25-30|
|--------|------------------------|------|------|------|------|------|
| T1.1 | P2, P3, P4, P5 |XXXXXX|XXXXXX|XXXXXX|XXX | |
| T1.2 | P3, P4 | XXX|XXXXXX| | | |
| T1.3 | P3, P4, P6 |XXXXXX|XXXXXX| | | |
| T1.4 | P2, P3, P4, P6 | | XXX|XXXXXX| | |
| T1.5 | P2, P3, P4, P5, P6 | | |XXXXXX|XXXXXX| |
|--------|------------------------|------|------|------|------|------|
| T2.1 | P2, P5 |XXXXXX|XXXXXX|XXXXXX|XXX | |
| T2.2 | P2, P5 | XXX|XXXXXX| | | |
| T2.3 | P1, P2, P3, P4, P5, P6 | | |XXXXXX|XXXXXX| |
|--------|------------------------|------|------|------|------|------|
| T3.1 | P2, P3, P4, P5 | | |XXXXXX| | |
| T3.2 | P3, P4, P6 | | |XXXXXX|XXXXXX| |
| T3.3 | P1, P2, P3, P4, P5, P6 | | | XXX|XXXXXX|XXXXXX|
|--------|------------------------|------|------|------|------|------|
| T4.1 | P1, P2, P3 |XXXXXX|XXXXXX|XXXXXX|XXXXXX| |
| T4.2 | P1, P2, P3 |XXXXXX|XXXXXX| | | |
| T4.3 | P1, P5 | |XXXXXX|XXX | | |
|--------|------------------------|------|------|------|------|------|
| T5.1 | P1, P2, P3, P4 | |XXXXXX|XXXXXX|XXXXXX|XXX |
| T5.2 | P1, P2, P3, P4 | | XXX|XXXXXX|XXXXXX|XXXXXX|
| T5.3 | P1, P3, P5 | | |XXXXXX|XXXXXX|XXXXXX|
| T5.4 | P1, P5 | | | XXX|XXXXXX|XXX |
----------------------------------------------------------------------