Issues

 / 

2009

 / 

January

  

Methodological notes


Direct observations of the viscosity of Earth’s outer core and extrapolation of measurements of the viscosity of liquid iron

 a,  b,  c
a Department of Earth and Space Science and Engineering, York University, 4700 Keele Street, Toronto, Ontario, M3J 1P3, Canada
b Institute for High Pressure Physics, Russian Academy of Sciences, Kaluzhskoe shosse 14, Troitsk, Moscow, 108840, Russian Federation
c Sander Geophysics Ltd., 260 Hunt Club Road, Ottawa, Ontario, K2P 1K2, Canada

Estimates vary widely as to the viscosity of Earth’s outer fluid core. Directly observed viscosity is usually orders of magnitude higher than the values extrapolated from high-pressure high-temperature laboratory experiments, which are close to those for liquid iron at atmospheric pressure. It turned out that this discrepancy can be removed by extrapolating via the widely known Arrhenius activation model modified by lifting the commonly used assumption of pressure-independent activation volume (which is possible due to the discovery that at high pressures the activation volume increases strongly with pressure, resulting in 102 Pa s at the top of the fluid core, and in 1011 Pa s at its bottom). There are of course many uncertainties affecting this extrapolation process. This paper reviews two viscosity determination methods, one for the top and the other for the bottom of the outer core, the former of which relies on the decay of free core nutations and yields 2371 ± 1530 Pa s, while the other relies on the reduction in the rotational splitting of the two equatorial translational modes of the solid inner core oscillations and yields an average of 1.247 ± 0.035 × 1011 Pa s. Encouraged by the good performance of the Arrhenius extrapolation, a differential form of the Arrhenius activation model is used to interpolate along the melting temperature curve and to find the viscosity profile across the entire outer core. The viscosity variation is found to be nearly log-linear between the measured boundary values.

Fulltext pdf (723 KB)
Fulltext is also available at DOI: 10.3367/UFNe.0179.200901d.0091
PACS: 66.20.−d, 91.35.−x, 93.85.−q (all)
DOI: 10.3367/UFNe.0179.200901d.0091
URL: https://ufn.ru/en/articles/2009/1/d/
000266708800004
2-s2.0-67849111476
2009PhyU...52...79S
Citation: Smylie D E, Brazhkin V V, Palmer A "Direct observations of the viscosity of Earth's outer core and extrapolation of measurements of the viscosity of liquid iron" Phys. Usp. 52 79–92 (2009)
BibTexBibNote ® (generic)BibNote ® (RIS)MedlineRefWorks

Оригинал: Смайли Д Е, Бражкин В В, Палмер А «Прямые наблюдения вязкости внешнего ядра Земли и экстраполяция измерений вязкости жидкого железа» УФН 179 91–105 (2009); DOI: 10.3367/UFNr.0179.200901d.0091

References (60) Cited by (22) ↓ Similar articles (9)

  1. Cormier V F, Bergman M I, Olson P L Earth’s Core (2022) p. 1
  2. Dmitriev A N, Pakharukov Yu V Izvestiâ Vysših Učebnyh Zavedenij. Neftʹ I Gaz (2) 39 (2021)
  3. Li Q, Sun T et al 155 (19) (2021)
  4. Luan W, Shen WenBin et al Surv Geophys 40 1129 (2019)
  5. Xian Jia‐Wei, Sun T, Tsuchiya T JGR Solid Earth 124 11105 (2019)
  6. Zhang Y, Nelson P et al JGR Solid Earth 124 10954 (2019)
  7. Costigliola L, Pedersen U R et al 148 (8) (2018)
  8. Adushkin V V, Spivak A A et al Dokl. Earth Sc. 474 579 (2017)
  9. Kanel’ G I, Savinykh A S et al High Temp 55 365 (2017)
  10. Meyer N, Xu H, Wax J -F Phys. Rev. B 93 (21) (2016)
  11. Mohazzabi P, Skalbeck J D International Journal Of Geophysics 2015 1 (2015)
  12. 汪 盼 CMP 04 134 (2015)
  13. Zarkevich N A, Johnson D D Phys. Rev. B 91 (17) (2015)
  14. Ding H, Chao B F JGR Solid Earth 120 7261 (2015)
  15. Peale S J, Margot Je-L et al Icarus 231 206 (2014)
  16. Seyed-Mahmoud B, Moradi A Physics Of The Earth And Planetary Interiors 227 61 (2014)
  17. Cao Q-L, Wang P-P et al 140 (11) (2014)
  18. Fomin Yu D, Ryzhov V N, Brazhkin V V J. Phys.: Condens. Matter 25 285104 (2013)
  19. Belashchenko D K Phys.-Usp. 56 1176 (2013)
  20. Ovtchinnikov V M, Kaazik P B, Krasnoshchekov D N Izv., Phys. Solid Earth 48 211 (2012)
  21. Zuberi M, Smylie D E Journal Of Geodynamics 48 230 (2009)
  22. Zharkov V N Uspekhi Fizicheskikh Nauk 179 106 (2009) [Zharkov V N Phys.-Usp. 52 93 (2009)]

© 1918–2024 Uspekhi Fizicheskikh Nauk
Email: ufn@ufn.ru Editorial office contacts About the journal Terms and conditions