Mie scattering by ensembles of particles with very large size parameters

Abstract

We present a computer program for the simulation of Mie scattering in case of arbitrarily large size parameters. The elements of the scattering matrix, efficiency factors as well as the corresponding cross-sections, the albedo and the scattering asymmetry parameter are calculated. Single particles as well as particle ensembles consisting of several components and particle size distributions can be considered. Program summary Title of program: miex Catalogue identifier: ADUD Program summary URL: http://cpc.cs.qub.ac.uk/summaries/ADUD Program obtainable from: CPC Program Library, Queen's University of Belfast, N. Ireland Computer for which the program is designed and others on which it has been tested: Computers: Any machine running standard FORTRAN 90; miex has been tested on an Intel Celeron processor (Redhat Linux 9.0, Intel Fortran Compiler 7.1), an Intel XEON processor (SuSE Linux 9.0, Intel Fortran Compiler 8.0), and a Sun-Blade-1000 (OS 8.5, Sun Workshop Compiler Fortran 90 2.0). Installations: standard Operating systems or monitors under which the program has been tested: Redhat Linux 9.0, SuSE Linux 9.0, Sun OS 8.5 Programming language used: Fortran 90 Memory required to execute with typical data: 1 MByte – several 100 MByte (see Appendix A for examples) No. of bits in a word: 8 No. of processors used: 1 Has the code been vectorized or parallelized?: No No. of lines in distributed program, including test data, etc.: 78 238 No. of bytes in distributed program, including test data, etc.: 1 015 805 Distributed format: tar.gz Nature of the physical problem: Among a variety of applications, Mie scattering is of essential importance for the continuum radiative transfer in cosmic dust configurations. In this particular case, Mie theory describes the interaction of electromagnetic radiation with spherical dust grains on the basis of their complex refractive index and size parameter. Both, broad grain size distributions (radii a: nanometers–millimeters) and a very wide wavelength range ( λ≈10 −10– 10 −2 m ) of the interacting radiation are considered. Previous numerical solutions to the Mie scattering problem are not appropriate to consider size parameters x=2 πa/ λ>10 4–10 5. In contrast to this, the presented code allows to consider arbitrary size parameters. It will be useful not only for applications in astrophysics but also in other fields of science (atmospheric and ocean optics, biophysics, etc.) and industry (particle sizing, ecology control measurements, etc.). Method of solution: Calculations of Mie scattering coefficients and efficiency factors as outlined by Voshchinnikov (2004), combined with standard solutions of the scattering amplitude functions. Single scattering by particle ensembles is calculated by proper averaging of the respective parameters. Restrictions on the complexity of the problem: Single scattering Typical running time: Seconds to minutes Unusual features of the program: None