T-matrix computations for particles with high-order finite symmetries
Journal article, 2013

The use of group theoretical methods can substantially reduce numerical ill-conditioning problems in T-matrix computations. There are specific problems related to obtaining the irreducible characters of high-order symmetry groups and to the construction of a transformation from the basis of vector spherical wave functions to the irreducible basis of high-order symmetry groups. These problems are addressed, and numerical solutions are discussed and tested. An important application of the method is non-convex particles perturbed with high-order polynomials. Such morphologies can serve as models for particles with small-scale surface roughness, such as mineral aerosols, atmospheric ice particles with rimed surfaces, and various types of cosmic dust particles. The method is tested for high-order 3D-Chebyshev particles, and the performance of the method is gauged by comparing the results to computations based on iteratively solving a Lippmann-Schwinger T-matrix equation. The latter method trades ill-conditioning problems for potential slow-convergence problems, and it is rather specific, as it is tailored to particles with small-scale surface roughness. The group theoretical method is general and not plagued by slow-convergence problems. The comparison of results shows that both methods achieve a comparable numerical stability. This suggests that for particles with high-order symmetries the group-theoretical approach is able to overcome the illconditioning problems. Remaining numerical limitations are likely to be associated with loss-of-precision problems in the numerical evaluation of the surface integrals.

Scattering

Cosmic dust

electromagnetic scattering

Mineral dust

formulation

T-matrix

Ice clouds

Author

Michael Kahnert

Chalmers, Earth and Space Sciences, Global Environmental Measurements and Modelling

Journal of Quantitative Spectroscopy and Radiative Transfer

0022-4073 (ISSN)

Vol. 123 79-91

Aerosol Optics in Global Earth System Modelling (AGES)

Swedish Research Council (VR) (2011-3346), 2011-10-26 -- 2014-10-26.

Subject Categories

Analytical Chemistry

DOI

10.1016/j.jqsrt.2012.08.004

More information

Created

10/6/2017