巻号一覧
44 巻, 3 号
選択された号の論文の7件中1～7を表示しています
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K. KAWASAKI, J. C. CAIN1992 年 44 巻 3 号 p. 167-180
発行日: 1992年
公開日: 2010/09/14
ジャーナル フリーHigh-latitude ionospheric and magnetospheric current systems are coupled via field-aligned currents (FACs). Because these highly temporal currents and associated fields are not fixed to geographic coordinates, analysis of satellite magnetic data by means of spherical harmonics has largely been restricted to periods of relative magnetic quiescence which are thought to be devoid of the effects of FACs. In principle, however, if a set of instantaneous (neglecting propagation time) worldwide satellite measurements were available, the fields of the vertical component of FACs could readily be removed from the satellite data, because they are not curl-free and thus they would not contribute to the spherical harmonic coefficients (SHCs) obtained in a spherical harmonic analysis (SHA) of the field. In this paper, some simple cases of radial currents and FACs with idealized ionospheric and magnetospheric closure currents are considered to show in what way sources internal and external to the satellite orbit would contribute to the internal and external terms of the spherical harmonic expansion. A method is then discussed for separating external and internal sources of the geomagnetic field in real satellite data, based on the non-curl free source conditions of FACs and the assumption that the distribution of the quiet-time ionospheric-magnetospheric coupling circuit and other sources of polar magnetic variations are a local geomagnetic time phenomenon.抄録全体を表示PDF形式でダウンロード (1573K) -
Vipin K. JAIN, Birbal SINGH1992 年 44 巻 3 号 p. 181-191
発行日: 1992年
公開日: 2010/09/14
ジャーナル フリーAnalysis of f0E data at Ahmedabad, India (geog. lat. 23°N, geomag. lat. -12°N, L-1.04) indicates average ionization enhancement of more than 10 percent during daytime following severe magnetic storms. This result is interpreted in terms of the precipitation of energetic particles under the charge exchange mechanism and excess ionization caused by solar EUV bursts. From a detailed calculations carried out for both the processes it is found that the contribution from charge exchange is more than 4% while that from EUV emissions is between 1-9%. This result indicates that although the contribution from the charge exchange mechanism is less, it is not insignificant even during daytime.抄録全体を表示PDF形式でダウンロード (946K) -
Hiroshi OKAMURA, Masaki EJIRI1992 年 44 巻 3 号 p. 193-205
発行日: 1992年
公開日: 2010/09/14
ジャーナル フリーIn order to study the detailed auroral spectral features that vary with a time, we have developed a new type of an auroral spectrometer which has a high time resolution. It can measure quantitatively a spectral apparent emission rate of aurora in a coordinate system of a wavelength and a spatial field of view of 72.6 degrees. A maximum time resolution, of course depending on an auroral luminous intensity, is 0.2sec. Observations with this instrument were carried out at Syowa Station, Antarctica, in 1989 austral winter. Preliminary results show various different spectral characteristics of aurora which, some cases, vary rapidly with a time.抄録全体を表示PDF形式でダウンロード (4462K) -
Hiromasa YAMAMOTO, Ichiro NAITO, Tadao MAKINO, Hiroyuki SEKIGUCHI1992 年 44 巻 3 号 p. 207-221
発行日: 1992年
公開日: 2010/09/14
ジャーナル フリーThe O2 1.27μm nightglow emission was observed by using a rocket-borne radiometer equipped with a high sensitive Ge sensor cooled by liquid nitrogen. The radiometer was flown on board the S-310-20 rocket launched at 04:30 JST, approximately 11 hours after local ground sunset, on January 28, 1990 from Kagoshima Space Center (31°N, 131°E), Japan. As the noise equivalent radiance at 1.27μm was only ±1.2kR when the time constant was 10ms, very fine data were obtained. The total zenith intensity was 207.1±2.4kR, which was 2-3 times as strong as those previously observed. The volume emission rate as a function of altitude showed two-layer structure, and the integrated intensity of a major layer centered at 92km was about 4 times as strong as that of the minor layer at 83km. The direct excitation by the three-body recombination of atomic oxygen could explain the emission of the major layer, when the excitation efficiency for O2(1Δg) is 0.75. The minor layer was found to be explained by an energy transfer from vibrationally excited OH to O2.抄録全体を表示PDF形式でダウンロード (1156K) -
A Case Study at Hohi Sugawara, Kyushu, JapanShinji TAKASUGI, Keisaku TANAKA, Noriaki KAWAKAMI, Shigeki MURAMATSU1992 年 44 巻 3 号 p. 223-242
発行日: 1992年
公開日: 2010/09/14
ジャーナル フリーOne defect of the MT method is its poor resolution of subsurface resistivity structure. We attempted to improve this situation by carrying out spatially continuous MT measurements along a straight line crossing a target area. Here we report the results of our measurements in the Hohi Sugawara area, central Kyushu, Japan. AMT data were also acquired at all the MT sounding sites. Comparison with logging data indicates that AMT data are necessary to estimate the shallow resistivity which is important for static correction in two-dimensional modeling. Analyses of MT data revealed some anomalous areas which seem to be closely related to the geothermal reservoir structure. If we incorporate other data such as logging data for geothermal wells, gravity data, and geological data, we can infer a more detailed reservoir structure.抄録全体を表示PDF形式でダウンロード (7448K) -
A Spherical Cap Harmonic Model of the Satellite Magnetic Anomaly Field Over China and Adjacent AreasZhen-chang AN, Shi-zhuang MA, Dong-hai TAN, D. R. BARRACLOUGH, D. J. K ...1992 年 44 巻 3 号 p. 243-252
発行日: 1992年
公開日: 2010/09/14
ジャーナル フリーUsing Magsat data over China and adjacent areas (between latitudes 10°N and 60°N and longitudes 70°E and 140°E), a spherical cap harmonic model describing the three-dimensional structure of the satellite magnetic anomaly field has been derived. The pole of the cap was at (35°N, 105°E), its half-angle was 35°and a maximum index of 12 was used. The maximum spherical harmonic degree corresponding to this index is 31.6, giving a minimum wavelength, at the Earth's surface, of 1266km. From this model and the International Geomagnetic Reference Field (IGRF), a model of the total intensity anomaly field (ΔF) was derived. The satellite magnetic anomalies (ΔX, ΔY, ΔZ, ΔF) at an altitude of 400km were calculated and the corresponding magnetic anomaly charts have been drawn.抄録全体を表示PDF形式でダウンロード (805K) -
M. ITONAGA, T.-I. KITAMURA, O. SAKA, H. TACHIHARA, M. SHINOHARA, A. YO ...1992 年 44 巻 3 号 p. 253-259
発行日: 1992年
公開日: 2010/09/14
ジャーナル フリーA Pi2 event observed simultaneously at three low-latitude and equatorial stations is analyzed using a new maximum likelihood method, and found to be mathematically composed of multiple exponentially damped sinusoids, of which frequencies are almost identical at the three stations. This is a piece of evidence to support the existence of the global mode cavity resonance. A numerical eigen-mode analysis of the decoupled poloidal wave equation with the outer boundary of the cavity located at the plasmapause can not sufficiently explain the observed discrete frequencies of the Pi2 event, so that the global cavity with the outer boundary outside the plasmapause is inevitably invoked.抄録全体を表示PDF形式でダウンロード (702K)
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