POLARIMETRIC PROPERTIES OF COMET AUSTIN

Model calculations have been made to explain the polarization observed during the passage of comet Austin. The observations were spread over four nights during the pre- and post-perihelion periods and were carried out at the IHW interference filters. The Austin data are compared with that of comet P/Halley reported in an earlier work (Sen et al.). The comparison, with the help of Mie theory, indicates that the polarizations in the two comets are probably caused by scattering due to two different types of grains, characterized by a change either in complex refractive index or size distribution or both. There are indications that comet Austin may contain finer grains as compared to P/Halley. Also a possible interpretation of these data with the help of scattering by large fluffy dark grains (Dollfus) is discussed.