@article{1266,
  author = {N. Weiss and J. Thomas and N. Brummell and S. Tobias},
  title = {The Origin of Penumbral Structure in Sunspots: Downward Pumping of Magnetic Flux},
  year = {2004},
  journal = {The Astrophysical Journal},
  volume = {600},
  pages = {1073-1090},
  month = {Oct-01-2004},
  issn = {0004-637X},
  url = {http://stacks.iop.org/0004-637X/600/i=2/a=1073},
  doi = {10.1086/380091},
}