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Paper: The Sun as a Rosetta Stone for Polarization Physics
Volume: 405, Solar Polarization 5: In Honor of Jan Olof Stenflo
Page: 3
Authors: Stenflo, J.O.
Abstract: The Sun has often been referred to as a Rosetta stone for astrophysics, since its proximity allows us to explore in detail the fundamental processes that govern the physics of objects in distant parts of the universe. Among these fundamental processes there was little attention given to polarization phenomena until about a decade ago, apart from various applications of the standard Zeeman effect for magnetic field diagnostics. With the implementation of new, highly sensitive imaging Stokes polarimeters a new and previously unfamiliar face of the Sun has been revealed, in the form of the richly structured Second Solar Spectrum. Its spectral structures are exclusively due to coherent scattering processes, which are modified by the partial decoherence caused by magnetic fields via the Hanle effect. The observed polarization phenomena are signatures of a rich variety of quantum-state superpositions, which in a unique way reconnects astrophysics with fundamental aspects of quantum theory. Here I choose to address this topic from a personal perspective, starting with some biographical notes and ending with some ideas on how current quantum scattering theory may need to be extended to explain the enigmatic polarization observed in the DI lines of sodium, barium, and potassium.
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