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Deep array electromagnetic sounding on the Baltic Shield: External excitation model and implications for upper mantle conductivity studies

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Title: Deep array electromagnetic sounding on the Baltic Shield: External excitation model and implications for upper mantle conductivity studies
Authors: Sokolova, Elena Yu. igemi3@mail.transit.ru, Varentsov, Ivan M.1
Source: Tectonophysics. Dec2007, Vol. 445 Issue 1/2, p3-25. 23p.
Subjects: Internal structure of the Earth, Ionosphere, Latitude, Magnetosphere
Abstract: Abstract: The BEAR array of simultaneous electromagnetic (EM) observations probes the deep crustal and upper mantle conductivity structure of the Baltic Shield searching for the lithosphere–asthenosphere boundary beneath. The adequate interpretation of the results of this unique high latitude natural field EM sounding requires proper understanding of the actual external excitation conditions because conventionally used plane wave model assumptions may be substantially violated in the vicinity of inhomogeneous polar sources. The paper presents an overview of the morphology and statistics of source distortions in the BEAR EM field transfer functions (TF) and the ways of their suppression. The stability of the final TF estimates obtained with the exclusion of intensive non-stationary auroral effects is further justified. The external excitation model effective for the whole BEAR observation period is inferred from the array distribution of the inter-station geomagnetic transfer functions. The model is supported by the results of polar ionosphere–magnetosphere current system studies, based on the simultaneous ground and satellite geomagnetic observations, and sets bounds for the “plane wave” approach in the BEAR data interpretation to avoid unfounded inferences on the upper mantle electrical properties. The signatures of the lithosphere–asthenospere boundary under Fennoscandia derived from the BEAR data are summarized and its resolution within the traditional plane wave interpretational paradigm is analysed assuming the presented external source pattern and estimated TF uncertainties caused by the source inhomogeneity. [Copyright &y& Elsevier]
Copyright of Tectonophysics is the property of Elsevier B.V. and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)
Database: Engineering Source
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DbLabel: Engineering Source
An: 27667376
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  Data: Deep array electromagnetic sounding on the Baltic Shield: External excitation model and implications for upper mantle conductivity studies
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  Data: <searchLink fieldCode="AR" term="%22Sokolova%2C+Elena+Yu%2E%22">Sokolova, Elena Yu.</searchLink><i> igemi3@mail.transit.ru</i><br /><searchLink fieldCode="AR" term="%22Varentsov%2C+Ivan+M%2E%22">Varentsov, Ivan M.</searchLink><relatesTo>1</relatesTo>
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  Data: <searchLink fieldCode="JN" term="%22Tectonophysics%22">Tectonophysics</searchLink>. Dec2007, Vol. 445 Issue 1/2, p3-25. 23p.
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  Data: Abstract: The BEAR array of simultaneous electromagnetic (EM) observations probes the deep crustal and upper mantle conductivity structure of the Baltic Shield searching for the lithosphere–asthenosphere boundary beneath. The adequate interpretation of the results of this unique high latitude natural field EM sounding requires proper understanding of the actual external excitation conditions because conventionally used plane wave model assumptions may be substantially violated in the vicinity of inhomogeneous polar sources. The paper presents an overview of the morphology and statistics of source distortions in the BEAR EM field transfer functions (TF) and the ways of their suppression. The stability of the final TF estimates obtained with the exclusion of intensive non-stationary auroral effects is further justified. The external excitation model effective for the whole BEAR observation period is inferred from the array distribution of the inter-station geomagnetic transfer functions. The model is supported by the results of polar ionosphere–magnetosphere current system studies, based on the simultaneous ground and satellite geomagnetic observations, and sets bounds for the “plane wave” approach in the BEAR data interpretation to avoid unfounded inferences on the upper mantle electrical properties. The signatures of the lithosphere–asthenospere boundary under Fennoscandia derived from the BEAR data are summarized and its resolution within the traditional plane wave interpretational paradigm is analysed assuming the presented external source pattern and estimated TF uncertainties caused by the source inhomogeneity. [Copyright &y& Elsevier]
– Name: AbstractSuppliedCopyright
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  Group: Ab
  Data: <i>Copyright of Tectonophysics is the property of Elsevier B.V. and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract.</i> (Copyright applies to all Abstracts.)
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      – Type: doi
        Value: 10.1016/j.tecto.2007.07.006
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      – Code: eng
        Text: English
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        PageCount: 23
        StartPage: 3
    Subjects:
      – SubjectFull: Internal structure of the Earth
        Type: general
      – SubjectFull: Ionosphere
        Type: general
      – SubjectFull: Latitude
        Type: general
      – SubjectFull: Magnetosphere
        Type: general
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      – TitleFull: Deep array electromagnetic sounding on the Baltic Shield: External excitation model and implications for upper mantle conductivity studies
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            NameFull: Sokolova, Elena Yu.
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            NameFull: Varentsov, Ivan M.
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              Text: Dec2007
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              Y: 2007
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              Value: 445
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