巻号一覧
47 巻, 7 号
選択された号の論文の6件中1～6を表示しています
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Hirokazu Minatoya, Natsuo Sato, Thorsteinn Saemundsson, Takeo Yoshino1995 年 47 巻 7 号 p. 583-598
発行日: 1995/07/20
公開日: 2007/04/03
ジャーナル フリーSimultaneous TV data of auroras were obtained at 3 nearly geomagnetic conjugate stations: Husafell in Iceland, and Syowa and Asuka in Antarctica, on September 9-10 in 1991. Active, pulsating auroras were found between 22:54 and 22:57 UT in both hemispheres. Pulsating spatial pattern, intensity variation, period and periodicity of periodic type pulsating auroras were used to examine possible conjugacy in the observational areas. The results reveal a distinct lack of correlation between pulsating auroras in geomagnetically conjugate stations during the event in question.抄録全体を表示PDF形式でダウンロード (2589K) -
S. Alex, D. R. K. Rao1995 年 47 巻 7 号 p. 599-606
発行日: 1995/07/20
公開日: 2007/04/03
ジャーナル フリーNon-regular features noticed in the quiet-time diurnal variation of H component on 11 December, 1990 (Ap = 2) and 12 December, 1990 (Ap = 7) in comparison with the average quiet day variations at a chain of equatorial, low and mid-latitude locations in the Indian longitude zone are studied. Stations away from the equatorial electrojet influence exhibited a minimum in the H field around 1600 LT followed by a secondary peak at 2100 LT. The globally observed anomalously enhanced variation in the “H” component at low and mid latitude is attributed to the effect of field aligned current driven by the magnetospheric plasma convection even during relatively quiet intervals. Causative mechanism to offset this peculiar feature, at equatorial locations is also discussed.抄録全体を表示PDF形式でダウンロード (1382K) -
S. L. Fontes, N. A. B. Seixas, I. Figueiredo, C. M. Motta1995 年 47 巻 7 号 p. 607-619
発行日: 1995/07/20
公開日: 2007/04/03
ジャーナル フリーIn this study is proposed an automatic computer algorithm for K-index evaluation for replacing the classical manual method. Our algorithm is based on the application of a second order Butterworth low-pass filter to daily records of the Earth's magnetic field. A variable filter cut-off frequency is analytically estimated as a function of three parameters: the observatory location, its scale value (in nT) for K = 9 and the peak-to-peak amplitude of the daily recorded signal. This variable cut-off frequency fitering (VCFF) procedure was tested for eleven observatories suggested by IAGA using records for the March-1985 February-1986 period. The Kcomp - Khand difference was used for checking the efficiency of the automatic method. A global absolute agreement of around 69%, i.e., Kcomp - Khand = 0, was achieved. For |Kcomp - Khand| = 1, the agreement reached 98%. These results are comparable to others reported in the literature.抄録全体を表示PDF形式でダウンロード (1791K) -
H. Rishbeth, S. Fukao1995 年 47 巻 7 号 p. 621-637
発行日: 1995/07/20
公開日: 2007/04/03
ジャーナル フリーThe MU radar is situated in a longitude sector very different from those of the American and European incoherent scatter radars. Its location, together with its unique operating characteristics, gives it a particular importance to worldwide studies of the thermosphere and ionosphere. This paper summarizes the MU radar's capability for studying the ionosphere at heights above 100 km (Section 1), and broadly reviews the principal results obtained in the first ten years of operation on the large-scale structure of the ionospheric E- and F-layers (Section 2); thermospheric winds, electric fields and gravity waves (Section 3); and field-aligned irregularities (Section 4). Data from other instruments in Japan, such as ionosondes and magnetometers, have proved vital to the interpretation of MU radar data.抄録全体を表示PDF形式でダウンロード (3656K) -
Tsuneji Rikitake1995 年 47 巻 7 号 p. 639-651
発行日: 1995/07/20
公開日: 2007/04/03
ジャーナル フリーMagnetic shielding by a spheroidal shell is studied. In order to see the shielding power of a flat shell in general, comparison between spheroidal, cylindrical and square shells is made in regard to shielding power. It is concluded that the flatter the shell becomes, the weaker is the shielding power. For the purpose of efficient shielding, we have to use a round shell that has no sharp edges and comers. It is doubtful that a flat case made of highly-permeable metal, that is on sale in the market, works as a shielding device for a floppy disk.抄録全体を表示PDF形式でダウンロード (1835K) -
Baldev R. Arora, Wallace H. Campbell, Edward R. Schiffmacher1995 年 47 巻 7 号 p. 653-665
発行日: 1995/07/20
公開日: 2007/04/03
ジャーナル フリーThe electrical conductivity profile of the Earth at depths of about 50 to 500 km was determined using the quiet ionospheric current variations observed at a line of stations near 75° East longitude. We found conductivity values of about 0.06 S/m from 50 to approximately 350 km depth with slight relative maxima near 125 and 275 kin, interpersed by relative minima near 210 and 330 km. Thereafter, the conductivity increased sharply toward a value of about 0.18 S/m at 500 km with no indication of leveling off. A comparison with regional seismic wave-velocity models shows good correspondence between high conductivity and low-velocity zones. The conduction by hydrogen-saturated pyroxene is envisaged as a possible mechanism for the high conductivity and its variation in the upper mantle.抄録全体を表示PDF形式でダウンロード (2866K)
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