This Working Group highlights the theoretical foundations of polarized radiation, as well as its numerical modelling as the essential link between theory and spectro-polarimetric observations. Therefore, it addresses the complex physics of the interaction of radiation and matter in magnetized plasmas, as well as the generation and transfer of polarized radiation. It deals also with the development and implementation of efficient numerical methods for making feasible realistic numerical simulations, as well as with polarized radiation diagnostics for determining the geometry and/or the physical properties of the astrophysical system under investigation.
Many different polarimetric instruments have been and are being constructed throughout Europe, and they have as many different science goals. There is therefore a wide range of expertise on polarimetric techniques and technology, which is not yet being fully exploited. Future instrument developments will certainly benefit from exchanging the various ideas on how to measure a specific polarization signal. This Working Group for the first time brings together instrumentalists and industrial partners, and stimulates cross-fertizilation between them. It constitutes a think-tank for novel polarimetric methods that is also available to the other Working Groups when they come up with ideas for new polarimetric science.
The goal of WG4 is to bring together people working on light scattering experiments with different setups (ground-based, on parabolic flights or space-based), using different wavelengths and aiming different targets (particles or surfaces, dust or ice, ...), in order to share the details of the techniques they use and their results.