Journal of geomagnetism and geoelectricity
Online ISSN : 2185-5765
Print ISSN : 0022-1392
ISSN-L : 0022-1392
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Volume 39, Issue 4
Displaying 1-6 of 6 articles from this issue
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  • Rename of Our Society
    Iwane Kimura
    1987 Volume 39 Issue 4 Pages 175
    Published: 1987
    Released on J-STAGE: September 14, 2010
    DOIhttps://doi.org/10.5636/jgg.39.175
    JOURNAL FREE ACCESS
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  • North-South Asymmetry in NmF2 at Mid-Latitude Conjugate Ionosphere Produced by Asymmetrical Thermospheric Winds
    Mehmet AYDOGDU
    1987 Volume 39 Issue 4 Pages 177-185
    Published: 1987
    Released on J-STAGE: September 14, 2010
    DOIhttps://doi.org/10.5636/jgg.39.177
    JOURNAL FREE ACCESS
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    Effects of the asymmetrical thermospheric winds on NmF2 at the latitudes 25°N, 35°N, 45°N and their geographically conjugate points have been computed for equinox conditions to study diurnal and longitudinal variations of the north-south differences in NmF2. In our calculations, the asymmetrical wind model of ILL et al. (1975) has been used. Although the effects of the winds on NmF2 are almost equal at latitudes 45°N and S, they give a significant effect on the north-south differences of NmF2 at lower latitude, namely NmF2 at latitudes 25°S and 35°S become about 30 percent greater than those at latitudes 25°N and 35°N between 02 and 08 LT (Local Time). This north-south asymmetry is most pronounced at each longitude around 06 LT. During the daytime, the maximum electron density of the F2-layer in the northern hemisphere becomes comparatively greater than the maximum electron density of the F2-layer in the southern hemisphere by the winds. In the evening, NmF2 at latitudes 25°S, 35°S, and 45°S are greater than NmF2 at their northern conjugate points in the longitude range 0°-120°E, reverse hold true in other longitude ranges. The computed differences in NmF2 between at latitudes 25°N, 35°N, 45°N and at their geographically conjugate points are in agreement with observational differences obtained by the ISS-B satellite, except during the nighttime at the longitude range 180°E-60°W. It is shown that the diurnal and longitudinal variations in the differences between NmF2 at mid-latitude point and those at its geographically conjugate point are well explained by considering the effects of the asymmetrical winds which focus toward the area of 02-05 LT, 35°N-40°N.
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  • Ionospheric Disturbances Induced by Substorm Associated Electric Fields in the Low-Latitude F-Region
    Tadatoshi TAKAHASHI, Hiroshi OYA, Shigeto WATANABE
    1987 Volume 39 Issue 4 Pages 187-209
    Published: 1987
    Released on J-STAGE: September 14, 2010
    DOIhttps://doi.org/10.5636/jgg.39.187
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    Based on the observation of low latitude ionosphere around 600km altitude by the Hinotori satellite, well-defined signatures of the ionospheric disturbances associated with substorm activities are found. In the wide area of the nightside equatorial region, a remarkable enhancement of local electron density takes place in response to the enhancement of the AE index, with a time delay shorter than the revolution period of the satellite (97min). The enhanced region is usually accompanied by several signatures which indicate the dynamical effects acting on the events, i.e. the development of the equatorial anomaly, longitudinal substructures and formation of the plasma bubbles. These signatures can be interpreted by dynamical uplift of the equatorial ionosphere. On the other hand, the equatorial anomaly is suppressed in dayside. Both of the nightside enhancement and the dayside suppression of the equatorial anomaly are induced simultaneously, although they are followed by rather different time sequential developments. The basic signatures of the ionospheric disturbance can be reasonably explained by dynamical effects of the disturbance electric field which is induced by substorm activities. The polarity of the disturbance electric field should be eastward in nightside and westward in dayside, and duration of the disturbance field is estimated to be about one hour or less.
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  • A Simultaneous Observation of the Height Profiles of the Night Airglow OI 5577Å, O2 Herzberg and Atmospheric Bands
    T. OGAWA, N. IWAGAMI, M. NAKAMURA, M. TAKANO, H. TANABE, A. TAKECHI, A ...
    1987 Volume 39 Issue 4 Pages 211-228
    Published: 1987
    Released on J-STAGE: September 14, 2010
    DOIhttps://doi.org/10.5636/jgg.39.211
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    Height distributions of the OI 5577Å, O2 Herzberg and Atmospheric bands in the night airglow were simultaneously measured with photometers on board a rocket flown from Uchinoura (31°N). The volume emission rates attained its maximum at a height of 96 km for the 5577Å, at 97km for the Herzberg bands and at 94km for the Atmospheric band, being in agreement with previous observations. The ratio of the volume emission rates of the Herzberg bands to the 5577Å exhibited a constant value with height, and that of the Atmospheric band to the 5577Å varied with height in proportion to the atmospheric density. Some implications to the excitation mechanism are presented and discussed according to this result along with the recent data on reaction rate coefficients from laboratory experiments.
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  • Paleomagnetic Implication on Climatic Changes and Evidence for Excursions Recorded in a Sediment Core from Harding Lake, Alaska
    Hayao MORINAGA, Kazuko S. MORINAGA, Katsumi YASKAWA
    1987 Volume 39 Issue 4 Pages 229-241
    Published: 1987
    Released on J-STAGE: September 14, 2010
    DOIhttps://doi.org/10.5636/jgg.39.229
    JOURNAL FREE ACCESS
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    Magnetic measurements have been performed on a lacustrine sediment core from Harding Lake, Interior Alaska, referring to lithofacies, granulometric features, pollen zones. The sediment core spans the approximate period 30, 000 to 2, 500 years B. P., on the basis of 14C dating. Sudden changes in the NRM intensity correspond to catastrophic timings of the past climate in Interior Alaska, which have inferred from pollen zones. Three anomalous directions exist in the sediment core. Two of them can be regarded as correspondents to the proposed geomagnetic excursions, “Starno” and “Gothenburg”, and the other is thought possibly to be a new excursion. The evidence suggesting the existence of any excursions between 26, 500 and 14, 000 years B. P. is not found in the present magnetic results, because of poor time coverage of each specimen in the identical period, 250 years.
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  • Book Review
    T. Terasawa
    1987 Volume 39 Issue 4 Pages 243-245
    Published: 1987
    Released on J-STAGE: August 11, 2011
    DOIhttps://doi.org/10.5636/jgg.39.243
    JOURNAL FREE ACCESS
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