Journal of geomagnetism and geoelectricity
Online ISSN : 2185-5765
Print ISSN : 0022-1392
ISSN-L : 0022-1392
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Volume 11, Issue 3
Displaying 1-4 of 4 articles from this issue
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  • Electromagnetic Induction in a Hemi-Spherical Ocean by Sq
    Tsuneji RIKITAKE
    1960 Volume 11 Issue 3 Pages 65-79
    Published: April 30, 1960
    Released on J-STAGE: September 14, 2010
    DOIhttps://doi.org/10.5636/jgg.11.65
    JOURNAL FREE ACCESS
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    A theory of electromagnetic induction within a hemi-spherical conducting sheet is described. The theory is applied to the induction by Sq in a large ocean of uniform depth bounded by two meridians. The patterns of the induced currents are obtained and illustrated both for the 24- and 12-hourly components. Unlike the previous theories, the effect of self-induction, which turns out to be rather important, is fully taken into account. The magnetic fields produced by the currents induced in the ocean amount to several gammas. The electric field in the sea associated with the induction would be of the order of mv/km.
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  • Physical State of Outer Atmosphere and the Origin of Radiation Belts
    Tatsuzo OBAYASHI
    1960 Volume 11 Issue 3 Pages 80-84
    Published: April 30, 1960
    Released on J-STAGE: September 14, 2010
    DOIhttps://doi.org/10.5636/jgg.11.80
    JOURNAL FREE ACCESS
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    A possible mechanism trapping high energy particles in the radiation belts surrounding the earth is proposed, taking into account the existing hydromagnetic waves in the outer atmosphere. It is shown that there are two regions where the amplitude of hydromagnetic waves and the compressibility of gas bearing magnetic field are large. Since the acceleration mechanism is operative in such regions, particles inside the regions may be raised in their energies, and consequently they produce local inhomogeneities of hot plasmas. These hot plasmas interact with the geomagnetic field and may form a certain kind of magnetic bottles, in which the high energy particles are likely trapped. The inner activated region is expected at the height 1, 000-3, 000km and the outer region is of the order of 20, 000km. Although the origin of high energy particles is possibly of injected solar particles, their concentration at particular regions may be controlled considerably by the hydromagnetic nature in the outer atmosphere.
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  • Magnetic Susceptibility of Some Rock Forming Silicate Minerals Such as Amphiboles, Biotites, Cordierites and Garnets
    Yasuhiko SYONO
    1960 Volume 11 Issue 3 Pages 85-93
    Published: April 30, 1960
    Released on J-STAGE: September 14, 2010
    DOIhttps://doi.org/10.5636/jgg.11.85
    JOURNAL FREE ACCESS
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    Some silicate minerals such as amphiboles, biotites, cordierites and garnets were examined magnetically. Magnetic susceptibility at the room temperature of garnets is in good agreement with the theoretical value estimated by using the effective Bohr magneton number derived empirically from salts bearing above magnetic ions, while in the case of amphiboles, biotites and cordierites, which contain water in their crystal structure, magnetic susceptibility at the room temperature shows fairly larger value than expected.
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  • Natural Occurrence of Titanomaghemite and Its Relevance to the Unstable Magnetization of Rocks
    Syun-iti AKIMOTO, Ikuo KUSHIRO
    1960 Volume 11 Issue 3 Pages 94-110
    Published: April 30, 1960
    Released on J-STAGE: September 14, 2010
    DOIhttps://doi.org/10.5636/jgg.11.94
    JOURNAL FREE ACCESS
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    Physical mechanism causing the scattered polarization or the unstable magnetization of some dolerite sheets was investigated through various magnetic measurements and microscopic observation. It was found from X-ray and chemical analyses that titanomaghemite exclusively occurs in the rocks showing unstable magnetization. This implies that the scattered polarization or the unstable magnetization of the rocks may be attributable to the following mechanism: the thermoremanent magnetization is destroyed by natural oxidation from original titanomagneite to titanomaghemite with the result that the remanent magnetization measured in the laboratory is only the isothermal remanent magnetization produced by the magnetic after effect under the geomagnetic field. The situations that the magnetic instability of rocks varies systematically according to the degree of the alteration or weathering were also elucidated.
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