Journal of geomagnetism and geoelectricity
Online ISSN : 2185-5765
Print ISSN : 0022-1392
ISSN-L : 0022-1392
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Volume 27, Issue 1
Displaying 1-7 of 7 articles from this issue
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  • Annual Modulation of Solar Diurnal Variation of the Cosmic Ray Nucleonic Component in Three-Dimensional Space
    Satoru MORI
    1975 Volume 27 Issue 1 Pages 1-23
    Published: 1975
    Released on J-STAGE: March 12, 2010
    DOIhttps://doi.org/10.5636/jgg.27.1
    JOURNAL FREE ACCESS
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    A study was made of the annual modulation of the cosmic ray solar diurnal variation to search one of the characteristics of the three-dimensional cosmic ray anisotropy in space. The present analysis, using the neutron monitor data from the worldwide network for the period of 1964-1968, is the extension work to confirm the results already derived from the meson data by Nagashima et al. In order to show the annual change of solar diurnal variations clearly, differences between the diurnal vectors at conjugate pairs of the observational stations in northern and southern hemispheres were exclusively utilized. A significant and systematic annual variation is found in the harmonic dial of monthly difference vectors moving in an ellipse having its major axis with the range of about 0.05% and the direction in 9hr of February-August in a year. This annual movement of solar diurnal variations can be interpreted in the framework of Nagashima's theory, due to the P12-type diurnal term arising from the second harmonic component of the cosmic ray solar anisotropy in space. The space distribution responsible for the annual variation of the nucleonic component is re-examined in terms of both solar and sidereal time variations.
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  • Electromagnetic Induction in the Earth When an Inducing Field is Modulated by Another Field of Longer Period
    Tsuneji RIKITAKE
    1975 Volume 27 Issue 1 Pages 25-32
    Published: 1975
    Released on J-STAGE: March 12, 2010
    DOIhttps://doi.org/10.5636/jgg.27.25
    JOURNAL FREE ACCESS
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    Geomagnetic variations of long period such as 0.5 year, 1 year and 11-years are customarily analyzed on the basis of monthly means of geomagnetic elements. As the geomagnetic field undergoes a 27-day variation which is modulated to some extent by an 11-year period variation, there is a possibility for the 11-year period variation to be contaminated by the effect of 27-day variation which may not be entirely eliminated through the procedure of taking monthly means. Such a leaking effect of shorter-period variation into longer-period ones in the geomagnetic field is discussed in this paper. The effect is small in most cases, but an appreciable effect seems likely to be seen in some cases, e. g. 30-day average of 27-day variation modulated by a semiannual variation.
    In actual analyses, the magnetic field electromagnetically induced in an earth model is calculated and subsequently subjected to the averaging procedure. Such a study brings out another point of interest. The relation between inducing and induced fields for a modulating field subjected to the averaging procedure becomes completely different from that when no short-period field is superposed. If one simply makes use of such a relation between inducing and induced field in estimating the electrical conductivity within the earth, a false conclusion will be reached.
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  • The Computation of Electric Currents Induced in the Oceans
    W. D. PARKINSON
    1975 Volume 27 Issue 1 Pages 33-46
    Published: 1975
    Released on J-STAGE: March 12, 2010
    DOIhttps://doi.org/10.5636/jgg.27.33
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    Price suggested two iterative methods of calculating the currents induced in the oceans by a given primary magnetic field. For a sub-storm field the actual earth lies outside the ranges of convergence of both methods. These ranges can be extended both by applying different iteration algorithms to the continents and oceans, and by using accelerators, but convergence is still not rapid enough to give useful results.
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  • Linear Magnetic Anomalies in the Shikoku Basin, Northeastern Philippine Sea
    Y. TOMODA, K. KOBAYASHI, J. SEGAWA, M. NOMURA, K. KIMURA, T. SAXI
    1975 Volume 27 Issue 1 Pages 47-56
    Published: 1975
    Released on J-STAGE: March 12, 2010
    DOIhttps://doi.org/10.5636/jgg.27.47
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    A linear magnetic pattern, offset along fracture zones was found in the Shikoku Basin, which lies between the Izu-Bonin and northern Kyushu-Palau Ridges. This lineation, nearly parallel to the trend of the Kyushu-Palau Ridge, seems to indicate that this basin originated from a type of seafloor spreading. A possible spreading center was suggested on the basis of symmetry of magnetic anomaly profiles and distribution of sediment cover in the basin. The anomaly profiles were tentatively correlated to the synthetic profile calculated from the reversal history of the earth's magnetic field during a period in Early to Middle Miocene, which gives a good fit of age to the result of the DSDP hole 297.
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  • Paleosecular Variation of Lavas from the Marianas in the Western Pacific Ocean
    U. S. -Japan Paleomagnetic Cooperation Program in
    1975 Volume 27 Issue 1 Pages 57-66
    Published: 1975
    Released on J-STAGE: March 12, 2010
    DOIhttps://doi.org/10.5636/jgg.27.57
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    A paleomagnetic study of 24 lava flows from Pagan Island (18.1°N, 145.7°E) in the Mariana Islands was conducted to determine the geomagnetic paleosecular variation in the Western Pacific. All flows are normally magnetized, and attempts to obtain radiometric ages for these flows were unsuccessful, and paleointensity determinations by the ‘Thellier method’ were unreliable. The mean virtual geomagnetic pole, (88°N, 110°W) is not significantly different from the rotation axis, suggesting that the lavas erupted over a period that spans at least several thousand years. The between-site angular dispersion SB, is used as a measure of the secular variation. SB=6.0° with respect to the mean VGP, and SB=6.2° with respect to the axis of rotation with a 95 percent confidence interval for the latter of 5.2°<SB<7.8°. Possible interpretations of the data include: (1) the sites studied represent an inadequate coverage in time; (2) the Marianas should be included in the Pacific dipole window; (3) there is a belt of average low angular dispersion encircling the earth between (roughly) 0° and 40°N.
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  • Geomagnetic Effects in the Dark Hemisphere Associated With Solar Flares
    J. Hanumath SASTRI, B. Suryanarayana MURTHY
    1975 Volume 27 Issue 1 Pages 67-73
    Published: 1975
    Released on J-STAGE: March 12, 2010
    DOIhttps://doi.org/10.5636/jgg.27.67
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  • Performance Tests of a Set of Gough-Reitzel Magnetic Variometers
    F. E. M. LILLEY, F. R. BURDEN, G. W. BOYD, M. N. SLOANE
    1975 Volume 27 Issue 1 Pages 75-83
    Published: 1975
    Released on J-STAGE: March 12, 2010
    DOIhttps://doi.org/10.5636/jgg.27.75
    JOURNAL FREE ACCESS
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