Much progress has been made in recent years in understanding the complex physics of polarized radiation in the sun and stars. This physics includes vector radiative transfer and spectral line formation in the presence of magnetic fields, scattering theory and coherence effects, partial redistribution and turbulent magnetic fields, numerical techniques and Stokes inversion, as well as concepts for polarimetric imaging with a precision limited only by photon statistics. The present volume gives a comprehensive and up-to-date account of this rapidly evolving field of science.

The scientific research based on spectropolarimetric techniques is undergoing a phase of rapid growth. Instruments of unprecedented sensitivity are nowadays available, particularly for solar observations. To fully exploit the rich diagnostic content of such observations, it is necessary to understand the physical mechanisms involved in the generation and transfer of polarized radiation in astrophysical (or laboratory) plasmas. After an introductory part based on classical physics, this book tackles the subject by a rigorous quantum-mechanical approach. The transfer equations for polarized radiation and the statistical equilibrium equations for the atomic density matrix are derived directly from the principles of Quantum Electrodynamics. The two sets of equations are then used to present a number of applications, mainly concerning the diagnostics of solar magnetic fields. This book is primarily addressed to scientists working in the field of spectropolarimetry. It may also serve as a textbook for a course at the graduate or advanced undergraduate level.

Novel instruments for high-precision imaging polarimetry have opened new possibilities, including for exploring effects in radiative scattering, atomic physics, spectral line formation, and radiative transfer. This volume gives a comprehensive and up-to-date account of this rapidly evolving and interdisciplinary field of science.

This book discusses analytic and asymptotic methods relevant to radiative transfer in dilute media, such as stellar and planetary atmospheres. Several methods, providing exact expressions for the radiation field in a semi-infinite atmosphere, are described in detail and applied to unpolarized and polarized continuous spectra and spectral lines. Among these methods, the Wiener–Hopf method, introduced in 1931 for a stellar atmospheric problem, is used today in fields such as solid mechanics, diffraction theory, or mathematical finance. Asymptotic analyses are carried out on unpolarized and polarized radiative transfer equations and on a discrete time random walk. Applicable when photons undergo a large number of scatterings, they provide criteria to distinguish between large-scale diffusive and non-diffusive behaviors, typical scales of variation of the radiation field, such as the thermalization length, and specific descriptions for regions close and far from boundaries. Its well organized synthetic view of exact and asymptotic methods of radiative transfer makes this book a valuable resource for both graduate students and professional scientists in astrophysics and beyond.