Journal of geomagnetism and geoelectricity
Online ISSN : 2185-5765
Print ISSN : 0022-1392
ISSN-L : 0022-1392
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Volume 35, Issue 9
Displaying 1-3 of 3 articles from this issue
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  • Observation of the Helium 10830Å Airglow Emission in Midlatitude
    Katsuhisa SUZUKI
    1983 Volume 35 Issue 9 Pages 321-330
    Published: 1983
    Released on J-STAGE: September 14, 2010
    DOIhttps://doi.org/10.5636/jgg.35.321
    JOURNAL FREE ACCESS
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    The helium 10830Å airglow in twilight was observed by a tilting filter photometer. Over three years observation reveals the seasonal variation and the solar zenith angle dependence of the helium emission. The enhancement of the emission was observed in winter. The solar zenith angle dependence was also investigated. The observation results show that the conjugate photoelectrons and the diurnal variation of the exsospheric temperature affect the helium emission.
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  • Source Current System of the Earth's Magnetic Non-Dipole Field
    Xi-Shuo WANG, Gui-Zhong QI
    1983 Volume 35 Issue 9 Pages 331-344
    Published: 1983
    Released on J-STAGE: September 14, 2010
    DOIhttps://doi.org/10.5636/jgg.35.331
    JOURNAL FREE ACCESS
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    Applying a matrix method of electromagnetic induction in a multi-layered earth to estimating the shielding effect of the earth conductor on geomagnetic secular change, we evaluated the source current system of the earth's magnetic non-dipole field which was separated into two parts, a standing field and a drifting one, by Yukutake and Tachinaka. To determine the radii of the source current shells we constructed a velocity model corresponding to the differential rotation of the fluid core by considering the skin effect and the charactristic drift velocity of the secular change. Thus located positions of the current shells are compatable with those from statistics. The energy dissipation estimated for each current shell is of the order of one-tenth to one-thousandth of that of the dynamo of the dipole field. A discussion concerning the resultant current system shows that the model, by which the earth's magnetic field has been separated into two parts, is acceptable.
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  • Matrix Method of Electromagnetic Induction in a Multi-Layered Spherical Medium and Shielding Effect of the Conducting Earth
    Xi-Shuo WANG, Gui-thong QI
    1983 Volume 35 Issue 9 Pages 345-356
    Published: 1983
    Released on J-STAGE: September 14, 2010
    DOIhttps://doi.org/10.5636/jgg.35.345
    JOURNAL FREE ACCESS
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    A matrix method dealing with electromagnetic induction in a spherically symmetric multi-layered medium is presented. The induction effects have been formulated as, X=U⋅(∏Dk)⋅Q and CJ=GJ⋅(∏Dk)⋅Q, where, the vector Q and C represent the electromagnetic fields outside and inside the conducting sphere, and X the current system of the source. The matrix U, Dk and GJ represent induction effects in the spherical layers. By this method the shielding effect due to a medium with spherical symmetry of electrical conductivity distribution can be precisely approximated and the fields within each layer of the sphere and the current system of the source can be conveniently evaluated from observation of the geomagnetic field at the earth's surface. An application is made to investigating the shielding effects of the conducting earth upon the source field of long-term geomagnetic variation for a 25-layered mantle model. The results show that for variations with period less than 720 years the mantle makes noted contribution to shielding effect and in order to estimate the effect of a fine-structured mantle a multi-layered model has to be considered.
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