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[1] We present measurements of the phase function and degree of linear polarization for unpolarized incident light as a function of the scattering angle for El Chichón and Pinatubo volcanic ashes at 633 nm. The results are combined and compared with those for Pinatubo at 442 nm and Lokon volcanic ash at 442 and 633 nm [Volten et al., 2001]. The three(More)
We discuss the composition and size distribution of the dust in the coma of comet Hale-Bopp. We do this using a model fit for the infrared emission measured by the infrared space observatory (ISO) and the measured degree of linear polarization of scattered light at various phase angles and wavelengths. The effects of particle shape on the modeled optical(More)
[1] We present measurements of the whole scattering matrix as a function of the scattering angle at a wavelength of 632.8 nm in the scattering angle range 3°–174° of randomly oriented particles taken from seven samples of volcanic ashes corresponding to four different volcanic eruptions: The samples were collected at different distances from the vent. The(More)
Record-low ozone (O3) column densities (with a minimum of 222 DU) were observed over the Lauder NDSC (Network for the Detection of Stratospheric Change) station (45 • S, 170 • E) in August 1997. Possible causes are examined using height-resolved O3 measurements over Lauder, and high-resolution reverse trajectory maps of O3 (initialised with Microwave Limb(More)
In this paper we study the combined effects of size and shape of small solid state particles on the absorption, emission and scattering characteristics. We use the statistical approach to calculate these optical properties. In this approach the average optical properties of an ensemble of particles in random orientation are represented by the average(More)
We model the 10 µm absorption spectra of nonspherical particles composed of amorphous silicate. We consider two classes of particles, compact ones and fractal aggregates composed of homogeneous spheres. For the compact particles we consider Gaussian random spheres with various degrees of non-sphericity. For the fractal aggregates we compute the absorption(More)
We provide a theoretical foundation for the statistical approach for computing the absorption properties of particles in the Rayleigh domain. We present a general method based on the Discrete Dipole Approximation (DDA) to compute the absorption and scattering properties of particles in the Rayleigh domain. The method allows to separate the geometrical(More)
The atmospheres of (exo) planets and moons, as well as reflection nebulae, contain in general independently scattering particles in random orientation and are often supposed to be plane-parallel. Relations are presented for the (bidirectional) reflection function and several related functions of such a medium in case the directions of incidence and(More)
We investigate the composition and shape distribution of silicate dust grains in the interstellar medium. The effects of the amount of magnesium and iron in the silicate lattice are studied in detail. We fit the spectral shape of the interstellar 10 µm extinction feature as observed towards the galactic center using various particle shapes and dust(More)
The elements of matrices relevant to polarized light transfer often obey certain equalities and inequalities that can be used for testing purposes. As an introduction to the reprint of our paper (Hovenier and van der Mee, 1996 [7]) we first present the case history and significance of this paper and then discuss some later developments. Studies of(More)