Scattering from Model Nonspherical Particles

Since the publication of the ?rst edition of this book, we have become deeply involved in astrophysics research, particularly the study of the interstellar medium. Modeling scattering particles as layered spheres or as aggregates of spherical scatterers, expanding the electromagnetic ?eld in a series of vector multipole ?elds, and resorting to the T-matrix approach for averaging over the orientations of a dispersion of nonspherical particles are e?ective tools for studying scattering theory, which we described and extensively applied in the ?rst edition of this book. In fact, these tools also proved to be adequate for studying cosmic dust, even when they must be applied to a new range of current problems. We refer, for example, to the description of mechanical interaction of electromagnetic radiation with cosmic dust grains, which is believed to be of paramount importance in determining the dynamics of the grains. Since this book is conceived as a summary of our work, the desire to encompassallnewtopicsledustorevisebothitscontentanditsstructure. Of course, beyond the changes that we outline below, all chapters were carefully revised. Marginal changes and additions were made in Chap. 1, while Chap. 2 has been substantially revised to cover the light of general polarization and, in particular, with thedescription ofthestate ofpolarization ofelectromagnetic waves of general form. In this chapter we reserved ample space for the r- resentation of the kinematics of the scattering processes both in the plane of scattering and in the meridional planes.

The scattering of electromagnetic radiation by nonspherical particles has become an increasingly important research topic over the past 20 years. Instead of handling anisotropic particles of arbitrary shape, the authors consider the more amenable problem of aggregates of spherical particles. This is often a very satisfactory approach as the optical response of nonspherical particles depends more on their general symmetry and the quantity of refractive material than on the precise details of their shape. The book addresses a wide spectrum of applications, ranging from scattering properties of water droplets containing pollutants, atmospheric aerosols and ice crystals to the modeling of cosmic dust grains as aggregates.

In this extended second edition the authors have encompassed all the new topics arising from their recent studies of cosmic dust grains. Thus many chapters were deeply revised and new chapters were added. The new material spans

• The description of the state of polarization of electromagnetic waves of general form
• The conservation theorems of combined systems of fields and particles
• The appropriate multipole expansion for waves of general wave vector and of general state of polarization
• A number of new applications
• The effects of radiation pressure and radiation torque on cosmic dust grains
  
• A study of the morphology of cosmic dust grains and of the distribution and polarization of the electromagnetic field in the interior of aggregated dust grains