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45 巻, 6 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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Takayuki Ono1993 年 45 巻 6 号 p. 455-472
発行日: 1993/06/20
公開日: 2007/04/03
ジャーナル フリーA high speed multi-channel photometer was operated at Syowa Station in Antarctica in 1990, to derive the energy spectrum ofprecipitating electrons through an intensity comparison of auroral emission lines and bands. The main purpose of this paper is to describe the instrumentation, the method of data analysis and preliminary results obtained by using the multi-channel photometer. Our observations showed that the intensity ratio of 844.6 nm (OI) line and 427.8 nm (N2+ 1PG) band is an useful indicator for an average energy of precipitating electrons, and a preliminary data analysis revealed the following results depending on the stage of auroral activity. i) An intense precipitation (several tens of erg/cm2/sec) of very low energy (about 100 eV) electrons was observed in association with a red aurora (called type-A red aurora) during a magnetic storm. ii) Switching signatures of the average energy as well as the total energy flux were observed for intense auroral pulsations. An auroral pulsation, observed for 630.0 nm (OI) emission line, was associated with a noticeable fluctuation in the average energy of precipitating electrons. iii) During the auroral break-up stage, individual intense arcs are associated with a significant increase of the precipitating electrons' average energy. The auroral lines of short wavelength (such as the 427.8 nm band used in the present observation) suffer from a scattering by the atmosphere, but we overcame this difficulty by measuring also the 670.5 nm (N2 1PG) auroral band emission.抄録全体を表示PDF形式でダウンロード (46724K) -
Masako Sasaki, Shu Takeshita, Masahisa Sugiura, Noriko Sudo, Yukiharu ...1993 年 45 巻 6 号 p. 473-485
発行日: 1993/06/20
公開日: 2007/04/03
ジャーナル フリーA new waterproof broadband UVB radiometer was designed to monitor biologically active solar UVB (290-320 nm) irradiance at ground level. Using this radiometer, solar UVB irradiance has been measured, together with UVA (320-400 nm) and Total (300-3300 nm) solar irradiances, for two years from October 1990 to September 1992. The global UVB solar irradiance shows clear seasonal changes, i.e., approximately by factors of 4 and 2 for the ratios of summer to winter and equinox to winter, respectively. In contrast, the seasonal variations in global UVA and Total are very similar and moderate in amplitude, and the corresponding ratios are about 1.7 and 1.3, respectively. Moreover, it is shown that the seasonal variation in the daily global UVB and that in the killing efficiency of sunlight for bacteriophage T1 have a similar pattern. For UVB and Total irradiances, the diffuse component was separately recorded. The monthly average ratio of the diffuse to the global (direct + diffuse) in UVB is persistently high, being about 80% throughout the year. The monthly average ratio of the diffuse to the global in Total solar irradiance was about 50% for the same period. Based on the present observation we found the 24-month average ratios of monthly global UVB/UVA/Total solar irradiance to be 0.14/4.1/100. Increases in the diffuse Total irradiance and in the global UVB irradiance, coupled with a decrease in the global Total irradiance, observed from November 1991 to February 1992 are interpreted as being an influence of the June 1991 eruption of Mt. Pinatubo.抄録全体を表示PDF形式でダウンロード (30397K) -
Masahiko Takeda1993 年 45 巻 6 号 p. 487-493
発行日: 1993/06/20
公開日: 2007/04/03
ジャーナル フリーEffects of the currents induced in the oceans on the geomagnetic field variations are estimated in the North Pacific region for the geomagnetic Sq field. At Honolulu, the amplitude of D-component is enhanced by 20% and that of Z-component decreases about 20% and the phase of Z-component are delayed by 2 hours, and the phase of Z-component are delayed by 2 hours. At Guam, the phase of the Z-component similarly delays, although the change of the amplitudes are smaller. On the other hand, there are no significant effects on the phases at Kakioka nor Kanoya in Japan. Therefore, the anomalous response at Kakioka cannot be explained by the ocean effect. It is shown that in middle North Pacific Ocean variations of westward and northward induced currents show nearly the same pattern with those of geomagnetic H- and D-components, respectively with slightly advanced phase. However, this relation does not hold true at the points near the fringe of the ocean because in the edge region of the oceans, currents are forced to flow parallel to the coasts and thus in the preferred direction.抄録全体を表示PDF形式でダウンロード (16291K) -
Guilin Yan, Shouyun Hu1993 年 45 巻 6 号 p. 495-502
発行日: 1993/06/20
公開日: 2007/04/03
ジャーナル フリーBased on that the order of magnitude of the anisotropy eigenvalue ratios of thermal remanent magnetization (TRM) is expected to be the square of the principal susceptibility ratios in anisotropic multidomain magnetic assemblages, a concrete correction formula is derived in this paper, which can be used to correct the TRM deviation induced by the anisotropy of magnetic susceptibility (AMS) away from the ambient field, and successfully applied to the practical paleomagnetic researches in Yueshan diorite (China) and Flamanville granite (France). An interesting discovery is that TRM direction is deflected away from that of the paleofield in each site. In contrast, the overall mean TRM direction is quite a good estimation of the paleofield direction, because the major axis of susceptibility ellipsoid are in the radial distribution.抄録全体を表示PDF形式でダウンロード (18439K) -
Desiderius C. P. Masalu, Kensaku Tamaki, Kazuo Kobayashi1993 年 45 巻 6 号 p. 503-534
発行日: 1993/06/20
公開日: 2007/04/03
ジャーナル フリーWe conducted a detailed bathymetric and magnetic total force survey of five seamounts in the Joban seamount chain during cruise KH90-1 of the R/V HAKUHO MARU in 1990. The Joban seamount chain is situated to the east of the southern Japan Trench, trends along N53°E (oblique to magnetic anomaly lineations whose trend is N68°) and extends over a distance of about 394 km. We applied three-dimensional magnetic inversion to each seamount. The three northern seamounts show relatively complex magnetization structures, whereas the two southern seamounts show simple magnetization structures. The latter yielded reliable results with VGPs (Virtual geomagnetic pole) at 55.5°N/348.9°E and 52.1°N/352.4°E. We estimated the ages of the two southern seamounts to be ca. 80 to 90 Ma by comparing their VGPs with known Pacific plate apparent polar wander path. We also estimated the ages for two guyot seamounts in the northern group to be ca. 110 to 130 Ma by backtracking their crests along crustal age-depth curve to sea level. The Joban seamount chain apparently shows presence of at least two groups of inclinations. This suggests that the origin of this seamount chain is not the passage of the Pacific plate over a single stationary hotspot.抄録全体を表示PDF形式でダウンロード (79484K) -
Kazuo Nagashima, Shizuko Sakakibara, Kazuhiko Fujimoto1993 年 45 巻 6 号 p. 535-538
発行日: 1993年
公開日: 2007/04/03
ジャーナル フリーIn the previous paper (NAGASHIMA et al., 1992), the authors pointed out the existence of the local-time-dependent precursory decrease of cosmic rays in front of the shock wave of the interplanetary magnetic field (IMF), and interpreted it as being due to their IMF-collimated outward flow across the shock from the inside of the Forbush decrease (Fd). In the present paper, they report its typical example recently observed in front of the Fd on September 9, 1992, as it bears the following dominant characteristics. The precursory decrease was not only exceedingly significant but also observed twice at the same station for two days running, which could not be clearly recognized in the previous analysis without taking the average of many events, and it was observed also with the underground muon telescope at Sakashita (depth: 80Hg/cm2), indicating its harder rigidity spectrum than the previous estimate. Based on these observations, the characteristics of the collimated flow responsible for the decrease is discussed.抄録全体を表示PDF形式でダウンロード (546K)
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