NONSPHERICAL DUST GRAINS IN THE ENVELOPES OF LATE-TYPE GIANTS

Effects of the grain shape on circumstellar dust dynamics and polariza tion of stellar radiation are analyzed. The grains are modeled by rota ting prolate and oblate spheroids. It is shown that an asymmetry of th e geometry of light scattering by non-spherical particles results in a component of the radiation pressure force (F) over right arrow(pr) pe rpendicular to the wave-vector of incident light. For silicate spheroi ds, this component can exceed 20% of \(F) over right arrow(pr)\ radiat ion pressure force for a spheroid can be 5-10 times greater than that for a sphere of the same volume. A simple light scattering considerati on demonstrates that the distinction in the scattering geometry of ali gned non-spherical grains can explain the observed wavelength variatio ns of the positional angle of polarization.