Journal of geomagnetism and geoelectricity
Online ISSN : 2185-5765
Print ISSN : 0022-1392
ISSN-L : 0022-1392
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Volume 24, Issue 4
Displaying 1-8 of 8 articles from this issue
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  • Lightning Discharge Studies in a Tropical Area
    III. The Profile of the Electrostatic Field Changes Due to Non-Ground Discharges
    Idowu AINA
    1972 Volume 24 Issue 4 Pages 369-380
    Published: 1972
    Released on J-STAGE: September 14, 2010
    DOIhttps://doi.org/10.5636/jgg.24.369
    JOURNAL FREE ACCESS
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    The electrostatic (e. s.) field changes due to lightning discharges which do not reach the ground have been studied at Ibadan. A discharge is in two stages similar to the predischarge and return stroke stages of a cloud-to-ground discharge. On the basis of this model the profiles of e. s. field changes have been worked out for the different discharges. These profiles explain all the observed e. s. field changes including the so-called complex field changes. The relatively short duration of the e. s. field change as compared with other parameters is also explained by the profiles.
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  • Lunar Magnetic Tides at Watheroo
    Seasonal, Elliptic, Evectional, Variational and Nodal Components
    D. E. WINCH, R. A. CUNNINGHAM
    1972 Volume 24 Issue 4 Pages 381-414
    Published: 1972
    Released on J-STAGE: September 14, 2010
    DOIhttps://doi.org/10.5636/jgg.24.381
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    Brief mathematical derivations of the various groups of terms in the tide-generating potential are given, and the resulting lunar magnetic tides and seasonal variations are tabulated. The inverse problem of relating lunar magnetic tides and the appropriate term in the tide-generating potential is then treated. Results for 36 different lunar magnetic tides computed from 40 years of hourly mean values recorded at the Watheroo magnetic observatory are presented.
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  • A Critical Study on the Reliability of Electron Temperature Measurements with a Langmuir Probe
    K. HIRAO, K. OYAMA
    1972 Volume 24 Issue 4 Pages 415-427
    Published: 1972
    Released on J-STAGE: September 14, 2010
    DOIhttps://doi.org/10.5636/jgg.24.415
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    Electron temperature deduced from a contaminated Langmuir probe is discussed. Laboratory and rocket experiments show that electron temperature evaluation is higher than the true value when the probe has a contaminated surface. It is concluded that the high temperature of the E-region is also due to the use of such a contaminated Langmuir probe. Hysteresis phenomenon can be explained by means of the simple equivalent circuit for the contamination layer of a probe surface.
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  • Equatorial Sporadic E Layer during Geomagnetic Storms
    R. G. RASTOGI
    1972 Volume 24 Issue 4 Pages 429-440
    Published: 1972
    Released on J-STAGE: September 14, 2010
    DOIhttps://doi.org/10.5636/jgg.24.429
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    The decrease of the average value of foEs at equatorial stations on disturbed days as compared to that on quiet days is shown to be due to frequent disappearance of Es(foEs<1MHz) during geomagnetic active periods rather than due to the decrease of individual values of foEs. The study of the q-type of Es during major SC-type geomagnetic storms indicates that there is no effect of a storm on Es-q so long as the change in the H field is less than that of the Dst(H) value. Only during large decreases in the H field exceeding the corresponding change in the Dst(H) value, the Es-q is shown to disappear completely. There is no apparent time lag between the decrease of H and the disappearance of Es. The Es-q can disappear even for a short period, for example, as five minutes. These effects are explained on the basis that Es-q is generated by the cross-field instability mechanism and its disappearance is due to temporary reversal of the electrojet current because of temporary imposition of a strong westward electric field over the normal Sq field.
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  • Magnetic Phase Relations of Pyrrhotite
    E. J. SCHWARZ, D. J. VAUGHAN
    1972 Volume 24 Issue 4 Pages 441-458
    Published: 1972
    Released on J-STAGE: September 14, 2010
    DOIhttps://doi.org/10.5636/jgg.24.441
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    A series of iron sulphide compositions containing between 50 and 46.0 atomic percent iron has been synthesized and the products of the syntheses annealed at 701, 350, 300 and 144°C. The charges were examined in polished sections by X-ray powder photography, electron microprobe analysis and Mossbauer spectroscopy, and the thermomagnetic properties were examined over a 25-350°C temperature range.
    The thermomagnetic data were used to construct a series of magnetic phase diagrams. Detailed information from these phase diagrams, together with information from the Mossbauer and X-ray studies, suggest that a series of discrete stoichiometric or near stoichiometric phases may occur at low temperatures. The FeS, Fe7S8 and Fe9S10 compositions appear to be such phases, and Fe10S11 and Fe11S12 may be further examples. These phases represent different vacancy ordering patterns and explain the frequent occurrence of two-phase intergrowths in natural pyrrhotites. The magnetic phase diagrams are required for the thermomagnetic analysis of finely intergrown natural pyrrhotites and also provide information relevant to the magnetic characteristics of pyrrhotite-containing ore bodies.
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  • The Stability of NRM of Deccan Traps Basalts in India
    H. KINOSHITA, Y. AOKI
    1972 Volume 24 Issue 4 Pages 459-470
    Published: 1972
    Released on J-STAGE: September 14, 2010
    DOIhttps://doi.org/10.5636/jgg.24.459
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    Samples of Deccan Trap basalts from all flows in the Mahabaleshwar and Amboli cliff sections in western India have been analysed by the thermomagnetic, and X-ray techniques. The principal conclusions are: 1) the NRM was stablized by oxidation of titanomagnetite shortly after eruption of lavas; 2) low-temperature oxidation of titanomagnetite can occur at ordinary temperatures is within a million years.
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  • Quiet Secular Variation in Japan during the Last 9500 Years
    Minoru OZIMA, Yutaka AOKI
    1972 Volume 24 Issue 4 Pages 471-477
    Published: 1972
    Released on J-STAGE: September 14, 2010
    DOIhttps://doi.org/10.5636/jgg.24.471
    JOURNAL FREE ACCESS
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  • Laboratory Emission of OI λ5577
    2. A Discharge Experiment on Oxygen and Hydrogen Gas Mixture
    Kunihiko WATADANI, Norio OGA
    1972 Volume 24 Issue 4 Pages 479-482
    Published: 1972
    Released on J-STAGE: September 14, 2010
    DOIhttps://doi.org/10.5636/jgg.24.479
    JOURNAL FREE ACCESS
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