This week's Physics magazine from the American Physical Society features an interesting article by Marric Stephens about an apparent anomaly - a contradiction between theoretical expectations and observational data regarding the sun's sodium D1 absorption line. Stephens reports on a new paper by a Swiss/Spanish/German team that resolves the paradox by replacing a seemingly reasonable assumption: that "the anisotropic radiation field that pumps the atoms of the solar atmosphere was assumed constant with wavelength over the very small spectral interval spanned by the nearby hyperfine structure components of both the sodium D1 and D2 lines." The authors Ballester, Belluzi, and Bueno apply a theory of polarized radiative transfer that takes "into account the detailed spectral structure of the radiation, together with the effects of magnetic fields of arbitrary strength and elastic collisions in a realistic atomic model including [hyperfine structure]" . There is a link to the paper itself, which is open source. A nice tale of resolving an apparent conflict between theory and observation.
Reference
Ballester, Belluzi, and Bueno, 2021, Phys. Rev. Lett. 127: 081101.
