POLARIZATION FROM SCATTERING IN BLOBS

We describe a Monte Carlo method for calculating polorization due to s cattering in various geometries. We apply the method in this paper to the case of scattering in a spherical cloud illuminated by parallel ra ys. The polarization is largest in small optical depth blobs, where si ngle scattering dominates. The polarization decreases as optical depth increases until a limit is reached where scattering occurs on the sur face, and increasing optical depth has little effect on the results. F or a given optical depth, decreasing the albedo leads to an increase o f the degree of polarization of the scattered light because single sca ttering increases relative to multiple scattering. As the optical dept h of the blob increases, the scattered flux becomes increasingly backw ard throwing. In the high albedo blobs, the maximum polarization becom es skewed towards the illuminated hemisphere at high optical depths. W e discuss the applications to polarization in supergaints and R CrB st ars, and scattering in a clumpy interstellar medium.