Quiet-day ionospheric currents and their application to upper mantle conductivity in Australia

• Campbell W. H.

  World Data Center A, NGDC/NOAA

• Barton C. E.

  Australian Geological Survey Organisation

• Chamalaun F. H.

  School of Earth Sciences, Flinders University of South Australia

• Welsh W.

  Australian Geological Survey Organisation

抄録

This study concerns the use of selected geomagnetic field records to establish the 1990 quiet-day current system (Sq) for Australia and to use the ionospheric current source of Sq for a determination of the Earth's deep electrical conductivity. The primary data set came from a chain of eight, three-component magnetometer stations that was operated along a north-south line in central Australia. Additional records, necessary for boundary conditions, were added to the data set. A regional spherical harmonic analysis (SHA) allowed the separation of the internal and external field contributions to the Sq variations. Mapping of the equivalent ionospheric current from the external field showed that the Sq contour focus passed near the -30° geomagnetic latitude of central Australia with a 5°latitude variation between winter and summer and a corresponding change from about 80 to 200 kA in strength. A special transfer function allowed the computation of an equivalent conductivity-depth profile of central Australia from the paired external and internal coefficients of the SHA. A regression line through the conductivity estimates gives a profile that starts at 0.025 S/m for a depth of 130 km, rising gradually to about 0.045 S/m at 250 km, then steepens to 0.11 S/m at 360 km and rises moderately to 0.13 S/m at 470 km near the base of the upper mantle. No data were obtained through the mantle transition zone. Computations gave 0.18 S/m in the region of 800 km depth. Previous conductivity models for the upper mantle beneath central Australia, although less specific in values, are consistent with our profile. At depths greater than 500 km, the regression profile is in agreement with the conductivity distribution beneath the Tasman Sea determined from seafloor magnetotellurics, although both measurements lack high resolution at such depths.

収録刊行物

• Ｅａｒｔｈ，　Ｐｌａｎｅｔｓ　ａｎｄ　Ｓｐａｃｅ

  Ｅａｒｔｈ，　Ｐｌａｎｅｔｓ　ａｎｄ　Ｓｐａｃｅ 50 (4), 347-360, 1998

  地球電磁気・地球惑星圏学会 、公益社団法人 日本地震学会、特定非営利活動法人 日本火山学会、日本測地学会、日本惑星科学会

キーワード

• Space and Planetary Science
• Geology

詳細情報

• CRID: 1390282681487138560
• NII論文ID: 10002206427
• NII論文ID: 130003955902
• NII書誌ID: AA11211921
• DOI: 10.1186/bf03352121
• ISSN: 18805981
• ISSN: 13438832
• Web Site: https://link.springer.com/content/pdf/10.1186/BF03352121.pdf
• Web Site: https://link.springer.com/article/10.1186/BF03352121/fulltext.html
• Web Site: http://link.springer.com/content/pdf/10.1186/BF03352121
• 本文言語コード: en
• データソース種別:
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  • Crossref
  • CiNii Articles
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