Archive: 2010 - Moldavian Journal of the Physical Sciences

05 Jun 2010

2010
V. 9
2
(p.199 - 204)

Upper mantle conductivity determined from the solar quiet day ionospheric currents in the dip equatorial latitudes of West Africa

Authors:

Obiekezie, T.; Okeke, F.

Summary:

The magnetic data obtained from a chain of ten magnetotelluric stations installed in the African sector during the international equatorial electrojet year (IEEY) was used to establish the 1993 quiet day current system (Sq) for West Africa and to determine the Earth’s upper mantle electrical conductivity in the region. A spherical harmonic analysis (SHA) was applied in the separation of the internal and external field/current contribution to the Sq variations, while a special transfer function was used to compute the conductivity – depth values from the paired external and internal coefficient of the SHA. The variation in the currents is seen to be a dawn to dusk phenomenon with the variation in the external currents different from that of the internal currents both in amplitude and in phase. The seasonal variation in the external current maximizes during the March equinox and minimizes in the December solstice. The conductivity had a downward increase with a high conductivity region spotted between 100 km and 205 km, which is seen to correspond to the seismic low velocity region. The conductivity at the upper mantle is seen to be 1.05 times higher than that obtained both in the Asian (Himalayan) and Australian regions.

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mantle electrical conductivity in the region. A spherical harmonic analysis (SHA) was applied 
in the separation of the internal and external  field/current contribution  to the Sq variations, 
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BibTeX

@article{ibn_4231,
author = {Obiekezie, T.N. and Okeke, F.N.},
title = {Upper mantle conductivity determined from the solar quiet day ionospheric currents in the dip equatorial latitudes of West Africa},
journal = {Moldavian Journal of the Physical Sciences},
year = {2010},
volume = {9 (2)},
pages = {199-204},
month = {Jun},
abstract = {(EN) The magnetic data obtained from a chain of ten magnetotelluric stations installed in the 

African sector during the international equatorial electrojet year (IEEY) was used to establish 
the 1993 quiet day current system  (Sq) for West Africa and to determine the Earth’s upper 
mantle electrical conductivity in the region. A spherical harmonic analysis (SHA) was applied 
in the separation of the internal and external  field/current contribution  to the Sq variations, 
while a special transfer function was used to compute the conductivity – depth values from 
the paired external and internal coefficient of the SHA. The variation in the currents is seen to 
be a dawn to dusk phenomenon with the variation in the external currents different from that 
of the internal currents both in amplitude and in phase. The seasonal variation in the external 
current maximizes during the March equinox and minimizes in the December solstice. The 
conductivity had a downward increase with a  high conductivity region spotted between 
100 km and 205 km, which is seen to correspond to the seismic low velocity region. The conductivity at the upper mantle is seen to be 1.05 times higher than that obtained both in the 
Asian (Himalayan) and Australian regions. 
 },
url = {https://ibn.idsi.md/vizualizare_articol/4231},
}

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African sector during the international equatorial electrojet year (IEEY) was used to establish 
the 1993 quiet day current system  (Sq) for West Africa and to determine the Earth’s upper 
mantle electrical conductivity in the region. A spherical harmonic analysis (SHA) was applied 
in the separation of the internal and external  field/current contribution  to the Sq variations, 
while a special transfer function was used to compute the conductivity – depth values from 
the paired external and internal coefficient of the SHA. The variation in the currents is seen to 
be a dawn to dusk phenomenon with the variation in the external currents different from that 
of the internal currents both in amplitude and in phase. The seasonal variation in the external 
current maximizes during the March equinox and minimizes in the December solstice. The 
conductivity had a downward increase with a  high conductivity region spotted between 
100 km and 205 km, which is seen to correspond to the seismic low velocity region. The conductivity at the upper mantle is seen to be 1.05 times higher than that obtained both in the 
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<dc:description xml:lang='en'>The magnetic data obtained from a chain of ten magnetotelluric stations installed in the 

African sector during the international equatorial electrojet year (IEEY) was used to establish 
the 1993 quiet day current system  (Sq) for West Africa and to determine the Earth’s upper 
mantle electrical conductivity in the region. A spherical harmonic analysis (SHA) was applied 
in the separation of the internal and external  field/current contribution  to the Sq variations, 
while a special transfer function was used to compute the conductivity – depth values from 
the paired external and internal coefficient of the SHA. The variation in the currents is seen to 
be a dawn to dusk phenomenon with the variation in the external currents different from that 
of the internal currents both in amplitude and in phase. The seasonal variation in the external 
current maximizes during the March equinox and minimizes in the December solstice. The 
conductivity had a downward increase with a  high conductivity region spotted between 
100 km and 205 km, which is seen to correspond to the seismic low velocity region. The conductivity at the upper mantle is seen to be 1.05 times higher than that obtained both in the 
Asian (Himalayan) and Australian regions. 
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<dc:source>Moldavian Journal of the Physical Sciences 9 (2) 199-204</dc:source>
<dc:title>Upper mantle conductivity determined from the solar quiet day ionospheric currents in the dip equatorial latitudes of West Africa</dc:title>
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“ ... ”

SM ISO690:2012

OBIEKEZIE, T.; OKEKE, F.. Upper mantle conductivity determined from the solar quiet day ionospheric currents in the dip equatorial latitudes of West Africa. In: Moldavian Journal of the Physical Sciences. 2010, nr. 2(9), pp. 199-204. ISSN 1810-648X.