Journal of geomagnetism and geoelectricity
Online ISSN : 2185-5765
Print ISSN : 0022-1392
ISSN-L : 0022-1392
Volume 27, Issue 3
Displaying 1-7 of 7 articles from this issue
  • Katsuhisa SUZUKI, Toshihiro OGAWA
    1975 Volume 27 Issue 3 Pages 175-186
    Published: 1975
    Released on J-STAGE: March 12, 2010
    JOURNAL FREE ACCESS
    The OI 6300 Å airglow in the morning twilight was observed with a high dispersion Ebert spectrometer. The 6300 Å emission could be detected against the background continuum due to Rayleigh scattering of the solar radiation with good accuracy for the solar zenith angle (SZA) larger than 96°. The O2 photodissociation may be the main excitation process for SZA=102°-98°; a theoretical calculation based on this excitation process can reproduce the observed 6300 Å intensity. The emission intensity observed shows a long-term variation in correlation with the solar activity, which may be caused by the variation of the thermospheric O2 density due to the variation of the thermopause temperature. A seasonal variation of the emission intensity, which shows large enhancement in winter, would be ascribed to the additional excitation by the local and conjugate photoelectron.
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  • Tadatoshi TAKAHASHI
    1975 Volume 27 Issue 3 Pages 187-200
    Published: 1975
    Released on J-STAGE: March 12, 2010
    JOURNAL FREE ACCESS
    The energy degradation of precipitating electrons with an energy range from 50eV to 600eV is investigated with special attention to the effect of anisotropic elastic collision. The discrete ordinate method is used for solving pitch angle distribution. It is found that pitch angle distribution of the penetrating fluxes are affected strongly by the phase function of scattering. The backscattered flux of several tenths of magnitude of the incident flux is obtained throughout energy range concerned. Pitch angle scattering due to elastic collision reduces the penetrating depth of electrons obtained in the case where only inelastic collisions are considered. Discussions on the validity of the discrete ordinate method are carried out.
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  • Osamu UCHINO, Motokazu HIRONO
    1975 Volume 27 Issue 3 Pages 201-215
    Published: 1975
    Released on J-STAGE: March 12, 2010
    JOURNAL FREE ACCESS
    On the basis of observational results with ruby laser radar (λ=6943 Å) backscattering and data on small ions, we examined typical stratospheric aerosol size distribution so far proposed.
    Power law size distribution and bimodal size distribution can explain both the laser radar backscattering coefficient and small ion density if we take into account the existence of numerous Aitken particles. Thus we cannot determine aerosol size distribution uniquely at the present stage of the investigations. We will examine here bimodal size distribution in some detail by considering the elementary physical processes.
    Power law size distribution, we suppose, is produced by in situ sulfuric acid particle nucleation. This size distribution is modified by increased outer particle injection such as a meteor particle or a volcanic eruption.
    When meteor particles are undergoing sedimentation, eddy diffusion, and growing by attachment of sulfuric acid particles which have a mean radius 5×10-3μm, assuming the power law size distribution, then meteor particle size distribution is lognormal. Bimodal size distribution is formed by both the lognormal size distribution and the preexisting Aitken size sulfuric acid particles.
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  • C. W. ANDERSON
    1975 Volume 27 Issue 3 Pages 217-232
    Published: 1975
    Released on J-STAGE: March 12, 2010
    JOURNAL FREE ACCESS
    The use of polarization parameters and amplitudes of spectral components of ULF pulsations observed at the earth's surface as diagnostics of magnetosphere dynamics can often be restricted because of the uncertainties of earth induction effects. The vertical component of the magnetic field, in particular, has been restricted in its use because of its well known sensitivity to the earth's conductive structure. In this paper Parkinson's method and the transfer function method, together with a heuristic approach to induction phenomena, are used to analyze the effects of earth induction on ULF pulsations observed along a latitudinal network of stations near L=4 in the northern hemisphere and in their conjugate region at Siple, Antarctica. Results indicate that earth induction has little effect on the characteristics of pulsations in the Pc3, Pc4 and Pc5 frequency bands at these stations. Preliminary results establish the existence of important temporal variations of the in-phase induction vectors at Girardville and LacRebours and their correlation with external source-field mechanisms.
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  • Tsuneji RIKITAKE
    1975 Volume 27 Issue 3 Pages 233-244
    Published: 1975
    Released on J-STAGE: March 12, 2010
    JOURNAL FREE ACCESS
    A quantitative evaluation of the geoelectric subterranean model beneath Japan is made on the basis of the analyses of short-period geomagnetic variations. For the model it has been surmised that the surface of a highly conducting mantle layer must steeply drop to a depth of 200km or so from a depth of 40-50km beneath the Pacific coast of central Japan. The depression seems likely to become shallower toward the Japan Sea underneath which the depth of the layer again reaches 40km.
    As the above “depression model” was derived on the basis of a perfect conductor approximation, it is important to see whether the model can account for the frequency characteristics of geomagnetic variation as brought out by intensive observations in recent years.
    The electromagnetic response of a conductive half-space having a triangular depression on its surface is estimated entirely numerically. Similar studies are also made for a case in which thin conductive sheets representing the sea are added. It turns out that the model seems likely to account for the characteristics of geomagnetic variations having a period range of a few tens of minutes. Although there is no guarantee for uniqueness, the depression model cannot be ruled out as a possible geoelectric structure beneath Japan.
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  • Shaul LEVI
    1975 Volume 27 Issue 3 Pages 245-255
    Published: 1975
    Released on J-STAGE: March 12, 2010
    JOURNAL FREE ACCESS
    Described are two slightly different procedures for performing the Thellier experiment (THELLIER and THELLIER, 1959). The first method is essentially that of COE (1967a, b), and the second is a slight modification thereof. The observed differences in the PNRM-PTRM curves are attributed to differences in the experimental procedure. The Coe method is preferred, as it is more symmetrical with respect to high temperature VRM and spontaneous decay and more likely to yield linear PNRM-PTRM plots.
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  • B. N. BHARGAVA, G. K. RANGARAJAN
    1975 Volume 27 Issue 3 Pages 257-263
    Published: 1975
    Released on J-STAGE: March 12, 2010
    JOURNAL FREE ACCESS
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