Published online by Cambridge University Press: 27 February 2018
The first scattering coefficient (a1-term) in Mie theory is introduced to determine the dipole polarizability used in the discrete dipole approximation (DDA) to calculate the scattering properties of the cluster of spheres in order to improve our understanding of interplanetary dust particles. In this method, each sphere in a cluster is replaced by a single dipole. The accuracy of this method is tested for a few spheres in contact. It is confirmed that the a1-term method is superior to other types of DDA and is particularly suitable for the case when the particles are placed randomly. By using this method, it becomes possible to treat large cluster of spheres, i.e., a size parameter of the target X(≡ 2πreq/λ) ∽ 50, where req is a volume equivalent radius of the target, and λ is the wavelength of incident wave.