Abstract
The Sun's visible spectrum is filled with a wealth of polarized spectral structures due to coherent scattering via bound-bound atomic transitions. Here we outline the theory for these coherence phenomena, including the effects of the external magnetic field (the Hanle effect), and demonstrate the correspondence between classical coherence and quantum interference between excited atomic states. Observational examples of the Hanle effect and of spectral features that can only be understood in terms of rather exotic quantum physics are presented. The signatures of coherent scattering have revealed the presence of a small scale, turbulent magnetic field in the Sun's photosphere, which has not been detectable by other techniques.
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