Solar-cycle effects on solar oscillation frequencies

@article{Libbrecht1990SolarcycleEO,
  title={Solar-cycle effects on solar oscillation frequencies},
  author={K. Libbrecht and M. Woodard},
  journal={Nature},
  year={1990},
  volume={345},
  pages={779-782}
}
Measurements of solar oscillations taken in 1986 and 1988 show systematic changes in the Sun's acoustic-mode frequencies of the order of 1 part in 10,000. These data reveal that the frequency shifts are the result of latitude-dependent changes in the structure of the Sun which are correlated with the Sun's magnetic-activity cycle. 
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