Interpretation of single-particle negative polarization at
intermediate scattering angles
J. Tyynelä*,1, E. Zubko1,2, K. Muinonen1,3 and G. Videen4
- 1 Department of Physics, University of Helsinki, P.O. box 14, FI-00014 Helsinki, Finland.
- 2 Astronomical Institute of Kharkov National University, 35 Sumskaya Street, Kharkov, Ukraine.
- 3 Finnish Geodetic Institute, P.O. box 15, FI-02431 Masala, Finland.
- 4 Army Res. Lab., AMSRD-ARL-CI-ES, 2800 Powder Mill Road, Adelphi, Maryland 20783, U.S.A.
We study how the internal field structure of irregular particles affects the far-field scattering characteristics by modifying the internal fields of the dipole groups that have the greatest contribution. We concentrate on the longitudinal component, i.e., the internal field component parallel to the incident wave vector. We use the discrete-dipole approximation to discretize the internal field and omit the longitudinal component from the dipoles that have the highest energy density above a preset cutoff value. We conclude that only a relatively small number of core dipoles, about 5% of all dipoles, contribute to the non-Rayleigh-type negative polarization at intermediate scattering angles. These core dipole groups are located at the forward part of the particles. The number of core dipoles in the group becomes greater as particle asphericity increases. We find that the interference between the core dipole groups, which was studied previously for spherical particles, is preserved to a large extent for non-spherical particles. We also find that the longitudinal component has little effect on both the degree of negative polarization and the depolarization ratio near backscattering.
- * Corresponding author