Journal of geomagnetism and geoelectricity

Latitudinal Extent of the Equatorial Electrojet

C. A. ONWUMECHILI, P. C. OZOEMENA

1985 年 37 巻 2 号 p. 193-204
発行日: 1985年
公開日: 2010/09/14

DOIhttps://doi.org/10.5636/jgg.37.193

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Theory is developed for estimating the latitudinal extent of the equatorial electrojet and the worldwide Sq currents including their return paths. It gives good estimates of the latitude of the worldwide Sq current focus as 36±2 degrees, and the latitudinal extent of the worldwide Sq current including its return paths as 84±3 degrees. The same model with the same procedure gives, for different longitudes, many values of the latitudinal extent of the equatorial electrojet including its return paths, with a mean of 784±30km. There is no systematic longitudinal variation of the latitudinal extent of the electrojet. The temporal variation of the latitudinal extent of the equatorial electrojet is similar to that of its half width and similarly it contracts when the electrojet is most intense at noon. The latitudinal extent of the residual electrojet decaying towards the night is however narrower at about 15hr. local time than the full electrojet around midday.

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Further Studies on Size Distribution of Siderophile Element Concentrations in Black Magnetic Spherules from Deep Sea Sediments

Kazuo YAMAKOSHI

1985 年 37 巻 2 号 p. 205-213
発行日: 1985年
公開日: 2010/09/14

DOIhttps://doi.org/10.5636/jgg.37.205

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(Co/Fe), (Ir/Fe) and (Au/Fe) ratios in magnetic iron spherules in deep sea sediments, whose sizes range from 16μm to 1440μm, were determined by instrumental neutron activation analysis. The following conclusion can be drawn from this work, together with the data obtained by a previous work for a narrow size region (100-440μum). Decreasing ratios of the respective element were commonly observed with increasing size of the spherules. In the intermediate size region (approximately 50-500μm), these ratios can be interpreted with the thermally degenerated compositions of metal phases of chondrites and iron meteorites. In the largest size region (>500μm), the spherules were so entirely oxidized that Co, Ir and Au components could hardly be detected. In the smallest size region (<50μm), we have many spherules, which had extremely high values of the ratios. The inner nucleus grains or nuggets of iron spherules, in which refractory or volatile elements were highly concentrated, is an available candidate for these spherules.

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Geomagnetic Inclination during Last 9, 000 Years Recorded in Sediment Cores from Lake Kasumigaura, Japan

Toshitsugu YAMAZAKI, Masato JOSHIMA, Yoshiki SAITO

1985 年 37 巻 2 号 p. 215-221
発行日: 1985年
公開日: 2010/09/14

DOIhttps://doi.org/10.5636/jgg.37.215

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