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지자기 변동성에 의해서 밝혀진 지구 핵 상부의 안정적인 층화 현상

Geomagnetic fluctuations reveal stable stratification at the top of the Earth’s core
  • 작성자 : KASI
  • 작성일 : 2014-04-01
  • 조회수 : 3509
  • 저자Bruce Buffett
  • Absract


    Modern observations of the geomagnetic field reveal fluctuations with a dominant period of about 60 years. These fluctuations are probably a result of waves in the liquid core4, although the precise nature of the waves is uncertain.Common suggestions include a type ofmagneticwave, known as a torsional oscillation5, but recent studies favour periods that are too short to account for a 60-year fluctuation. Another possibility involvesMACwaves, which arise fromthe interplay betweenmagnetic, Archimedes and Coriolis forces.Waves with a suitable period can emerge when the top of the core is stably stratified. Here I show that MAC waves provide a good description of time-dependent zonal flow at the top of the core, as inferred from geomagnetic secular variation. The same wave motion can also account for unexplained fluctuations in the dipole field10. Bothof these independent predictions require a 140-kilometre-thick stratified layer with a buoyancy frequency comparable to the Earth’s rotation rate.Such a stratified layer could have a thermal origin,implying a core heat flow of about 13 terawatts. Alternatively, the layer could result from chemical stratification. In either case, the existence of a stratified layer at the top of the core obscures the nature of flow deeper in the core, where the magnetic field is continually regenerated.

     

     

     



     


  • 게재정보Nature(2014.3.27)에 실린 천문학 분야의 연구논문을 게시함
  • 첨부파일
  • 원 문http://www.nature.com/nature/journal/v507/n7493/full/nature13122.html
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