Journal of geomagnetism and geoelectricity
Online ISSN : 2185-5765
Print ISSN : 0022-1392
ISSN-L : 0022-1392
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Volume 33, Issue 8
Displaying 1-3 of 3 articles from this issue
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  • A Semidiurnal Wind Oscillation with Short Vertical Wavelength Observed in the Tropical Lower Stratosphere
    Shoichiro FUKAO, Yasuyuki MAEKAWA, Susumu KATO
    1981 Volume 33 Issue 8 Pages 421-427
    Published: 1981
    Released on J-STAGE: March 12, 2010
    DOIhttps://doi.org/10.5636/jgg.33.421
    JOURNAL FREE ACCESS
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    Radar measurement of the tropical lower stratosphere at Jicamarca (12°S) reaffirmed the existence of a semidiurnal wind oscillation similar to that detected foremost at Arecibo (18°N), which has a vertical wavelength as short as 10km and a horizontal wind amplitude of 0.2-1ms-1. It seems very important that the two measurements made in different hemispheres detect a similar type of semidiurnal oscillation, being significantly different from global tidal oscillations.
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  • Self Reversed Thermoremanent Magnetization in a Late Brunhes Dacite Pumice
    Lawrence P. KENNEDY
    1981 Volume 33 Issue 8 Pages 429-448
    Published: 1981
    Released on J-STAGE: March 12, 2010
    DOIhttps://doi.org/10.5636/jgg.33.429
    JOURNAL FREE ACCESS
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    The reversed NRM component of a dacite pumice has the same magnetic properties as a self-reversed TRM component produced by laboratory induction. The reversed TRM is therefore attributed to self-reversal, not to a geomagnetic reversal. X-ray diffraction indicates the presence of titanomagnetite and an α-(Fe, Ti)2O3 mineral with intermediate composition. The model offered by Ishikawa and Syono (1963) to describe the self-reversal mechanism in α-(Fe, Ti)2O3 with intermediate composition is applicable. The Ferich metastable phase produced during ordering in α-(Fe, Ti)2O3 represents the initial stages of the exsolution process. Exsolution-unmixing of an iron-enriched phase aids ordering in the remainder of the mineral by increasing its titanium content. Distinct cooling regimes, imposed by mode of emplacement and by local variations in volume or thickness of a volcanic unit, are responsible for different annealing conditions. These factors may account for the differences in the properties of the self-reversed magnetization of the Natib and Haruna dacite pumices and the variation of their characteristics.
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  • High-Pressure Apparatus for Use with a Cryogenic Magnetometer
    S. J. PIKE, T. L. HENYEY, J. REVOL, M. D. FULLER
    1981 Volume 33 Issue 8 Pages 449-466
    Published: 1981
    Released on J-STAGE: March 12, 2010
    DOIhttps://doi.org/10.5636/jgg.33.449
    JOURNAL FREE ACCESS
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    A high-pressure cell designed to be compatible with a cryogenic magnetometer is described. The cell is used to perform experiments requiring simultaneous application of uniaxial and confining stresses at elevated temperature on specimens of up to 2.6cm diameter. The primary application of the cell is to simulate conditions which may prevail in the earth's upper crust prior to an earthquake. The cryogenic magnetometer is used to measure accompanying changes in sample magnetization.
    Operation and perfomance of the pressure cell/magnetometer system is illustrated with data from non-magnetic specimen tests and one granitic rock sample representative of basement lithologies near the San Andreas fault system in southern California.
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