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4 results on '"DISCRETE RANDOM-MEDIA"'

1. Scattering of light by a large, densely packed agglomerate of small silica spheres

Author

E. Hadamcik, Karri Muinonen, Jérémy Lasue, Jean-Baptiste Renard, Jürgen Blum, Timo Väisänen, Anny Chantal Levasseur-Regourd, Johannes Markkanen, Laboratoire de Physique et Chimie de l'Environnement et de l'Espace (LPC2E), Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), Planetary-system research, Department of Physics, Department of Physics [Helsinki], Falculty of Science [Helsinki], University of Helsinki-University of Helsinki, Max-Planck-Institut für Sonnensystemforschung (MPS), Max-Planck-Gesellschaft, PLANETO - LATMOS, Laboratoire Atmosphères, Milieux, Observations Spatiales (LATMOS), Sorbonne Université (SU)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National d’Études Spatiales [Paris] (CNES), Institut de recherche en astrophysique et planétologie (IRAP), Institut national des sciences de l'Univers (INSU - CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Observatoire Midi-Pyrénées (OMP), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS), Institut für Geophysik und Extraterrestrische Physik [Braunschweig] (IGEP), Technische Universität Braunschweig = Technical University of Braunschweig [Braunschweig], Finnish Geospatial Research Institute (FGI), The PROGRA2 instrument, Helsingin yliopisto = Helsingfors universitet = University of Helsinki-Helsingin yliopisto = Helsingfors universitet = University of Helsinki, Max-Planck-Institut für Sonnensystemforschung = Max Planck Institute for Solar System Research (MPS), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), and Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS)

Subjects
Materials science, Scanning electron microscope, [SDU.ASTR.EP]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], 02 engineering and technology, 01 natural sciences, Molecular physics, 114 Physical sciences, Light scattering, 010309 optics, Optics, RADIATIVE-TRANSFER, 0103 physical sciences, PARTICLES, ComputingMilieux_MISCELLANEOUS, [PHYS.PHYS.PHYS-AO-PH]Physics [physics]/Physics [physics]/Atmospheric and Oceanic Physics [physics.ao-ph], Linear polarization, Scattering, business.industry, RAY OPTICS, 021001 nanoscience & nanotechnology, Atomic and Molecular Physics, and Optics, Particle aggregation, [SPI.ELEC]Engineering Sciences [physics]/Electromagnetism, Agglomerate, Degree of polarization, SPHERES, 0210 nano-technology, business, DISCRETE RANDOM-MEDIA, MONTE-CARLO SIMULATIONS, APPROXIMATION
Abstract

We model the measured phase function and degree of linear polarization of a macroscopic agglomerate made of micrometer-scale silica spheres using the methodology of multiple scattering. In the laboratory work, the agglomerate is produced ballistically, characterized by scanning electron microscopy, and measured with the PROGRA 2 instrument to obtain the light scattering properties. The model phase function and degree of polarization are in satisfactory agreement with the experimental data. To our best knowledge, this is the first time the degree of linear polarization has been modeled well for a large, densely packed agglomerate composed of small particles with known sizes and shapes. The study emphasizes the relevance of the degree of linear polarization and gives insights into the effects of particle aggregation on the scattering characteristics.

Published
2020
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2. Absolute spectral modelling of asteroid (4) Vesta

Author

Maria Gritsevich, Karri Muinonen, Julia Martikainen, Gorden Videen, Antti Penttilä, and Department of Physics

Subjects
010504 meteorology & atmospheric sciences, NUMERICAL [METHODS], DIVERSITY, 01 natural sciences, methods: numerical, REGOLITH, MINOR PLANETS, 0103 physical sciences, SCATTERING, PHOTOMETRY, Spectroscopy, INDIVIDUAL: VESTA [ASTEROIDS], 010303 astronomy & astrophysics, 0105 earth and related environmental sciences, Physics, SPECTROSCOPY, METEORITES, Scattering, SPECTROSCOPIC [TECHNIQUES], scattering, Astronomy, Astronomy and Astrophysics, DAWN, 115 Astronomy, Space science, Regolith, Photometry (astronomy), Meteorite, Space and Planetary Science, Asteroid, Physics::Space Physics, MAIN-BELT, Astrophysics::Earth and Planetary Astrophysics, DISCRETE RANDOM-MEDIA, minor planets, asteroids: individual: Vesta, techniques: spectroscopic
Abstract

We present a new physics-based approach to model the absolute reflectance spectra of asteroid (4) Vesta. The spectral models are derived by utilizing a ray-optics code that simulates light scattering by particles large compared to the wavelength of the incident light. In the light of the spectral data obtained by the Dawn spacecraft, we use howardite powder to model Vesta's surface regolith and its particle size distribution for 10-200 μm sized particles. Our results show that the modelled spectrum mimics well the observations. The best match was found using a power-law particle size distribution with an index 3.2. This suggests that Vesta's regolith is dominated by howardite particles

Published
2018
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3. Radiative transfer with reciprocal transactions: Numerical method and its implementation

Author

Karri Muinonen, Antti Penttilä, Johannes Markkanen, Timo Väisänen, Particle Physics and Astrophysics, Planetary-system research, and Department of Physics

Subjects
Albedo, Atmospheric Science, Light, 010504 meteorology & atmospheric sciences, Monte Carlo method, Astronomical Sciences, Optical Analysis, 01 natural sciences, Light scattering, T-MATRIX, Scattering, Electricity, Radiative transfer, Scattering, Radiation, Statistical physics, EQUATIONS, 010303 astronomy & astrophysics, Climatology, Physics, Multidisciplinary, Refractive Index, Planetary Sciences, Applied Mathematics, Simulation and Modeling, Electromagnetic Radiation, Software Engineering, EM WAVES, SPHERES, Mie Scattering, Electric Field, Physical Sciences, MULTIPLE-SCATTERING, Engineering and Technology, Medicine, DISCRETE RANDOM-MEDIA, Electromagnetic Phenomena, Algorithms, Reciprocal, Research Article, Computer and Information Sciences, Mie scattering, Science, Electromagnetic Scattering, Research and Analysis Methods, 114 Physical sciences, Superposition principle, 0103 physical sciences, Computer Simulation, Chemical Characterization, 0105 earth and related environmental sciences, Numerical analysis, Light Scattering, Source Code, Earth Sciences, Focus (optics), Mathematics
Abstract

We present a numerical method for solving electromagnetic scattering by dense discrete random media entitled radiative transfer with reciprocal transactions ((RT2)-T-2). The (RT2)-T-2 is a combination of the Monte Carlo radiative-transfer, coherent-backscattering, and superposition T-matrix methods. The applicability of the radiative transfer is extended to dense random media by incorporating incoherent volume elements containing multiple particles. We analyze the (RT2)-T-2 by comparing the results with the asymptotically exact superposition T-matrix method, and show that the (RT2)-T-2 removes the caveats of radiative-transfer methods by comparing it to the RT-CB. We study various implementation choices that result in an accurate and efficient numerical algorithm. In particular, we focus on the properties of the incoherent volume elements and their effects on the final solution.

Published
2019

4. Rigorous light-scattering simulations of nanophase iron space-weathering effects on reflectance spectra of olivine grains

Author

Julia Martikainen, Karri Muinonen, Antti Penttilä, Johannes Markkanen, Timo Väisänen, Gorden Videen, Tomas Kohout, Department of Physics, Particle Physics and Astrophysics, Planetary-system research, Department of Geosciences and Geography, and Geology and Geophysics

Subjects
Materials science, 010504 meteorology & atmospheric sciences, ASTEROIDS, Mineralogy, 114 Physical sciences, 01 natural sciences, Space weathering, Spectral line, Light scattering, The moon, 0103 physical sciences, Spectral slope, ABSORPTION, NANOPARTICLES, PARTICLES, 010303 astronomy & astrophysics, Spectroscopy, 0105 earth and related environmental sciences, Astronomy and Astrophysics, RAY OPTICS, Spectral bands, Albedo, WAVELENGTHS, 115 Astronomy, Space science, Regolith, Wavelength, Space and Planetary Science, LASER IRRADIATION EXPERIMENTS, MERCURY, Regoliths, DISCRETE RANDOM-MEDIA
Abstract

We present a multi-scale light-scattering model that is capable of simulating the reflectance spectra of a regolith layer. In particular, the model can be applied to a case where the regolith grains have varying amounts of nanophase inclusions due to space weathering of the material. As different simulation tools are employed for different size scales of the target geometry (roughly, nano-, micro-, and millimeter scales), the particle size effects, the surface reflections, and the volume scattering can all be properly accounted for. Our results with olivine grains and nanophase iron inclusions verify the role of the nanoinclusions in the reflectance spectra of space-weathered materials. Together with the simulation results, we give simplified explanations for the space-weathering effects based on light scattering, namely the decrease of albedo, the general increase of the red spectral slope, and the dampening of the spectral bands. We also consider the so-called ultraviolet bluing effect, and show how the change in the spectral slope over the ultraviolet-visual wavelengths is due to the decrease of reflectance in the visual wavelengths rather than the increase of reflectance in the ultraviolet part.

Published
2020
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