Origin of Sunspots

@article{Menzel1950OriginOS,
  title={Origin of Sunspots},
  author={Donald Howard Menzel},
  journal={Nature},
  year={1950},
  volume={166},
  pages={31-32}
}
ALTHOUGH astronomers have commonly believed that sunspots are deep-seated vortices, the chief characteristics of a spot (an intense magnetic field and a cool umbra) have never been successfully explained. 
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