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T-matrix computations for particles with high-order finite symmetries

Michael Kahnert (Institutionen för rymd- och geovetenskap, Global miljömätteknik och modellering)
Journal of Quantitative Spectroscopy and Radiative Transfer (0022-4073). Vol. 123 (2013), p. 79-91.
[Artikel, refereegranskad vetenskaplig]

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.

Nyckelord: Scattering, T-matrix, Mineral dust, Cosmic dust, Ice clouds, electromagnetic scattering, formulation

Denna post skapades 2013-06-27. Senast ändrad 2014-02-03.
CPL Pubid: 179407


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Institutioner (Chalmers)

Institutionen för rymd- och geovetenskap, Global miljömätteknik och modellering (2010-2017)



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Denna publikation är ett resultat av följande projekt:

Aerosol Optics in Global Earth System Modelling (AGES) (VR//2011-3346)