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Paper: Unsolved Problems in Solar Polarization
Volume: 437, Solar Polarization Workshop 6
Page: 3
Authors: Stenflo, J. O.
Abstract: The Second Solar Spectrum has presented us with a rich and unfamiliar world of polarization phenomena. While the many new spectral structures have great diagnostic potential, they cannot be exploited before we have identified the underlying physical processes and formulated a theory for them. This theoretical challenge has led to considerable advances in our understanding of the interaction between matter and radiation in magnetized media, but a number of observed polarization phenomena remain unexplained. Cases like the enigmatic Na I D1 line indicate serious gaps in our understanding. A problem has been the lack of benchmarks, against which the quantum theory of polarized scattering can be tested. Polarized light scattering was a hot experimental topic in the early years of quantum physics until about 1935, after which the quantum physicists turned to other topics. A recent laboratory experiment to explore the physics of the enigmatic D1 scattering transition has exposed the failure of the currently used theory and prompted intense efforts to search for remedies. Besides these issues with scattering polarization we discuss other unsolved problems like the magnetic structuring on spatially unresolved scales. There are also enigmas for the global magnetic field of the Sun. In the final section we expose a case where Hale's polarity law is being violated.
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