Mie and Debye scattering in dusty plasmas

We calculate the total held scattered by a charged sphere immersed in a pla sma using a unified treatment that includes the usual Mie scattering and th e scattering by the Debye cloud around the particle. This is accomplished b y use of the Dyadic Green function to determine the held radiated by the el ectrons of the Debye cloud, which is then obtained as a series of spherical vector wave functions similar to that of the Mie field. Thus we treat the Debye-Mie field as a whole and study its properties. The main results of th is study rue (1) the Mie (Debye) field dominates at small (large) wavelengt hs and in the Rayleigh limit the Debye held is constant; (2) the total cros s section has an interference term between the Debye and Mie fields, import ant in some regimes; (3) this term is negative for negative charge of the g rain, implying a total cross section smaller than previously thought; (4) a method is proposed to determine the charge of the grain (divided by a cert ain suppression factor) and the Debye length of the plasma; (5) a correctio n to the dispersion relation of an electromagnetic wave propagating in a pl asma is derived.