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Scattering at dust and ice particles

We simulate the scattering of electromagnetic fields at dust and ice particles as found in industrial environments but even more in interplanetary space.

Related publications by the TET group


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Light scattering by 3-Foci convex and concave particles in the geometrical optics approximation

D. Stankevich, L. Hradyska, Y. Shkuratov, Y. Grynko, G. Videen, J. Förstner, Journal of Quantitative Spectroscopy and Radiative Transfer (2019)

We consider light scattering from a new type of model particle whose shape is represented in the form of a generalized ellipsoid having N foci, where N is greater than two. Such particles can be convex as well as concave. We use the geometrical optics approximation to study the light scattering from 3-foci particles. Non-zero elements of the scattering matrix are calculated for ensembles of randomly oriented independent transparent particles, m = n + i0. Several internal reflection orders are considered separately. It was found that the transmission-transmission (TT) and transmission-reflectance-transmission (TRT) components dominate in the formation of intensity of scattered light at large and small phase angles, respectively. We found a significant role of the total internal reflections of the TRT in the middle portion of the phase angle range. The main factors in the formation of positive linear polarization are the R and TRT component. The TT component is responsible for the formation of negative polarization branch at large phase angles.


    Intensity surge and negative polarization of light from compact irregular particles

    Y. Grynko, Y. Shkuratov, J. Förstner, Optics Letters (2018), 43(15)

    We study the dependence of the intensity and linear polarization of light scattered by isolated particles with the compact irregular shape on their size using the discontinuous Galerkin time domain numerical method. The size parameter of particles varies in the range of X = 10 to 150, and the complex refractive index is m = 1.5 + 0i. Our results show that the backscattering negative polarization branch weakens monotonously, but does not disappear at large sizes, up to the geometrical optics regime, and can be simulated without accounting for wave effects. The intensity backscattering surge becomes narrower with increasing particle size. For X = 150, the surge width is several degrees.


      Radar backscattering from a large-grain cometary coma: numerical simulation

      S. Dogra, Y. Grynko, E. Zubko, J. Förstner, Astronomy & Astrophysics (2017), 608

      We numerically simulate the circular polarization ratio of the radar signal backscattered from a large-grain cometary coma and compare the simulation results with the radar measurements for seven comets. We apply the discrete dipole approximation method and a model of random irregular particles. Our results confirm water ice composition of the cm-sized chunks detected by the NASA Deep Impact space probe in the vicinity of the nucleus of Comet 103P/Hartley 2. The index of the power-law size distribution in this case can be constrained to the range n ≈ 3.3–4.3. For the other considered comets the circular polarization ratio can be reproduced with variations of the power index between 2 and 5.


      Comparison between the physical-optics approximation and exact methods solving the problem of light scattering by ice crystals of cirrus clouds

      A.V. Konoshonkin, N.V. Kustova, A.G. Borovoi, H. Okamoto, K. Sato, H. Ishimoto, Y. Grynko, J. Förstner, in: 22nd International Symposium on Atmospheric and Ocean Optics: Atmospheric Physics, SPIE, 2016

      In the problem of light scattering by ice crystals of cirrus clouds, two exact methods (FDTD – finite difference time domain and DGTD – discontinuous Galerkin time domain) and the physical-optics approximation are used for numerical calculations of the Mueller matrix in the case of ice hexagonal plates and columns. It is shown that for the crystals larger than 10 μm at the wavelength of 0.532 μm the exact methods and physical-optics approximation closely agreed within three diffraction fringes about the centers of the diffraction patterns. As a result, in the case of random orientation of these crystals, the physical-optics approximation provides accuracy 95% for the averaged Mueller matrix.


        Light scattering by ice crystals of cirrus clouds: From exact numerical methods to physical-optics approximation

        A. Konoshonkin, A. Borovoi, N. Kustova, H. Okamoto, H. Ishimoto, Y. Grynko, J. Förstner, Journal of Quantitative Spectroscopy and Radiative Transfer (2016), 195, pp. 132-140

        The problem of light scattering by ice crystals of cirrus clouds is considered in the case of a hexagonal ice plate with different distributions over crystal orientations. The physical-optics approximation based on (E, M)-diffraction theory is compared with two exact numerical methods: the finite difference time domain (FDTD) and the discontinuous Galerkin time domain (DGTD) in order to estimate its accuracy and limits of applicability. It is shown that the accuracy of the physical-optics approximation is estimated as 95% for the averaged backscattering Mueller matrix for particles with size parameter more than 120. Furthermore, the simple expression that allows one to estimate the minimal number of particle orientations required for appropriate spatial averaging has been derived.


          Light scattering by irregular particles much larger than the wavelength with wavelength-scale surface roughness

          Y. Grynko, Y. Shkuratov, J. Förstner, Optics Letters (2016), 41(15)

          We simulate light scattering by random irregular particles that have dimensions much larger than the wavelength of incident light at the size parameter of 𝑋=200 using the discontinuous Galerkin time domain method. A comparison of the DGTD solution for smoothly faceted particles with that obtained with a geometric optics model shows good agreement for the scattering angle curves of intensity and polarization. If a wavelength-scale surface roughness is introduced, diffuse scattering at rough interface results in smooth and featureless curves for all scattering matrix elements which is consistent with the laboratory measurements of real samples.


            Light scattering by ice crystals of cirrus clouds: comparison of the physical optics methods

            A.V. Konoshonkin, N.V. Kustova, A.G. Borovoi, Y. Grynko, J. Förstner, Journal of Quantitative Spectroscopy and Radiative Transfer (2016), 182, pp. 12-23

            The physical optics approximations are derived from the Maxwell equations. The scattered field equations by Kirchhoff, Stratton-Chu, Kottler and Franz are compared and discussed. It is shown that in the case of faceted particles, these equations reduce to a sum of the diffraction integrals, where every diffraction integral is associated with one plane–parallel optical beam leaving a particle facet. In the far zone, these diffraction integrals correspond to the Fraunhofer diffraction patterns. The paper discusses the E-, M- and (E, M)-diffraction theories as applied to ice crystals of cirrus clouds. The comparison to the exact solution obtained by the discontinuous Galerkin time domain method shows that the Kirchhoff diffraction theory is preferable.


              Light scattering by randomly irregular dielectric particles larger than the wavelength

              Y. Grynko, Y. Shkuratov, J. Förstner, Optical Letters (2013), 38(23), pp. 5153-5156


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              Contact

              Dr. Yevgen Grynko

              Theoretical Electrical Engineering

              Yevgen Grynko
              Phone:
              +49 5251 60-3815
              Fax:
              +49 5251 60-3524
              Office:
              P 1.5.02.2

              Head of the group

              Prof. Dr. Jens Förstner

              Theoretical Electrical Engineering

              Jens Förstner
              Phone:
              +49 5251 60-3013
              Fax:
              +49 5251 60-3524
              Office:
              P1.5.01.1

              Office hours:

              on request (during lecture break)

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