IEEJ Transactions on Fundamentals and Materials
Online ISSN : 1347-5533
Print ISSN : 0385-4205
ISSN-L : 0385-4205
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Volume 126, Issue 4
Displaying 1-11 of 11 articles from this issue
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Special Issue on Recent Progress in Seismo-Electromagnetics
Special Issue Review
Special Issue Paper
  • Multifractal Analysis for the ULF Geomagnetic Data during the Guam Earthquake
    Yu-ichi Ida, Masashi Hayakawa, Kaoru Gotoh
    2006 Volume 126 Issue 4 Pages 215-219
    Published: 2006
    Released on J-STAGE: July 01, 2006
    DOIhttps://doi.org/10.1541/ieejfms.126.215
    JOURNAL FREE ACCESS
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    In our previous papers we have shown that the fractal (monofractal) dimension (Do) showed a significant increase before the Guam earthquake occurred on August 8, 1993. In order to have a further support to this precursory effect, we have carried out the corresponding multifractal analysis (by means of detrended fluctuation analysis) for the same data to study the statistical self-similar properties in a wide range of scales. We have analyzed the ULF geomagnetic data (the most intense H component) observed at Guam observatory. As the result, we have found that we could observe significant changes in the multifractal parameters at Guam. αmin showed a meaningful decrease about 25 days before the earthquake, but αmax exhibited no significant change at all, so that Δα showed a significant increase before the earthquake. Correspondingly, the generalized multifractal dimension Dq (q>1) showed a significant decrease (whereas Dq (q<0) showed no change) and D0 (= Dq (q=0) (as already found in our previous papers) is reconfirmed to increase before the earthquake. These multifractal characteristics seem to be a further support that these changes are closely associated with the earthquake as a precursor to the Guam earthquake.
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  • A Statistical Study on the Dependence of Characteristics of VLF/LF Terminator Times on the Propagation Direction
    Shinko Maekawa, Masashi Hayakawa
    2006 Volume 126 Issue 4 Pages 220-226
    Published: 2006
    Released on J-STAGE: July 01, 2006
    DOIhttps://doi.org/10.1541/ieejfms.126.220
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    We present a detailed statistical study over two years on the times of amplitude minima (so-called terminator times) observed for the VLF/LF transmitters NPM/NWC/JJY as received at three sites. We analyzed three paths: East-West long propagation path, North-South long propagation path and North-South short propagation path. In this paper we examine the statistical behavior on the dependence of VLF/LF terminator time characteristics on the propagation direction and also we focus on the short-term terminator time (TT) characteristics. We found from the data analysis that TT behavior is regularly influenced by the lower-ionospheric condition which depends on the sunrise/sunset transition and season.
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  • Satellite Data Analysis System for Searching Microwave Emission Associated with Earthquakes
    Takashi Maeda, Tadashi Takano, Kozaburo Inoue, Teruo Kato
    2006 Volume 126 Issue 4 Pages 227-232
    Published: 2006
    Released on J-STAGE: July 01, 2006
    DOIhttps://doi.org/10.1541/ieejfms.126.227
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    Recently it was experimentally shown that rock crash by static pressure caused the microwave emission, and this result suggests the microwave would be emitted on the occasion of earthquakes. In order to verify this hypothesis, we have developed the computer system for analyzing the huge satellite database of Institute of Space and Astronautical Science (ISAS). The database includes the orbital parameters and the communication data of all satellites launched by ISAS. As a result, we have found out some anomalies in the data of the S-band (2GHz) microwave power level as for ASCA satellite by this system.
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  • The Relationship between the Current through the Transformer Neutral Point and Natural Phenomena
    Jun Izutsu, Takashi Ochi, Tomiichi Uetake, Tatsuya Mutakamihigashi
    2006 Volume 126 Issue 4 Pages 233-237
    Published: 2006
    Released on J-STAGE: July 01, 2006
    DOIhttps://doi.org/10.1541/ieejfms.126.233
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    The neutral points of the transformers in substations are grounded and connected by the power lines. By measuring the current which flows through the neutral points, the telluric current between substations could be measured. We have monitored this current in order to detect anomalies before and after earthquakes since 1996. Although the neutral current is theoretically zero, it is generated by various factors, such as temperature and geomagnetic changes, and artificial noises. A very large change of the neutral current, unexplainable by these factors, was observed before and after the M3.0 earthquake which occurred under the power lines on September 22, 1999. However, so far, we have never observed any anomalies for other earthquakes.
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  • Spatial Distribution of Source Locations of Earth-origin Electromagnetic Pulses Excited before Earthquakes
    Minoru Tsutsui, Takeshi Maenishi
    2006 Volume 126 Issue 4 Pages 238-241
    Published: 2006
    Released on J-STAGE: July 01, 2006
    DOIhttps://doi.org/10.1541/ieejfms.126.238
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    In order to find a possibility of earth-origin electromagnetic (EM) pulses as a precursor of earthquakes, we attempted to obtain spatial distributions of source locations of many EM pulses detected two days before earthquakes. In this paper, we first introduce the procedure for obtaining their source locations, which consists of determinations of exact arrival directions of the EM pulses, estimations of their propagation distances and identifications of their source locations. In deriving a spatial distribution of their locations, we found that the EM pulse sources had been drifting during the period of about 6 hours. The area of the spatial distribution of their source locations was rather small but far from the earthquake epicenter. The spatial difference between the EM pulse source locations and the earthquake epicenter is discussed from view points of conditions for excitations and propagations of EM pulses.
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Special Issue Letter
Paper
  • Observations of Transient Luminous Events from Earth Orbit
    Yoav Yair
    2006 Volume 126 Issue 4 Pages 244-249
    Published: 2006
    Released on J-STAGE: July 01, 2006
    DOIhttps://doi.org/10.1541/ieejfms.126.244
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    We review the results of space-based observations of Transient Luminous Events occurring in the upper atmosphere in conjunction with intense lightning flashes. The global rate of these events has significant implications on the global electrical circuit, combining the lower troposphere with the ionosphere. The needed TLE climatology can be best addressed by orbiting space platforms. The results from various such platforms are presented: from early Space Shuttle missions, the MEIDEX campaign, the LSO on-board the ISS and unmanned instruments on the FORMOSAT-2 and RHESSI satellites. Future missions are briefly described.
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  • Numerical Study on Gain Coefficient of a Capillary-Discharged Neon-Like Argon X-Ray Laser
    Majid Masnavi, Mitsuo Nakajima, Kazuhiko Horioka
    2006 Volume 126 Issue 4 Pages 250-255
    Published: 2006
    Released on J-STAGE: July 01, 2006
    DOIhttps://doi.org/10.1541/ieejfms.126.250
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    X-ray laser gain of J = 0 → 1 transition (λ = 46.9nm) in collisionally pumped neon (Ne)-like argon (Ar IX) ion has been investigated considering 37 levels of the 2p6, 2p53s, 2p53p, 2p53d, 2s2p63s, 2s2p63p, and 2s2p63d configurations. The effect of radiative trapping of resonance lines on the gain coefficient is studied using a collisional radiative model and a one-dimensional single-fluid, two-temperatures magnetohydrodynamic (MHD) equations. Results indicate that the gain value is significantly affected by the plasma opacity, and the velocity gradient allows us to obtain a higher gain in collisionally pumped Ne-like ions excited in fast capillary-discharged plasmas.
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  • A Study of Upward Positive Leaders Based on Simultaneous Observation of E-Fields and High-Speed Images
    Nobuyuki Takagi, Daohong Wang, Teiji Watanabe
    2006 Volume 126 Issue 4 Pages 256-259
    Published: 2006
    Released on J-STAGE: July 01, 2006
    DOIhttps://doi.org/10.1541/ieejfms.126.256
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    We have measured the correlated sub-microsecond E-fields and high-speed images of nine upward positive leaders occurred in winter from high grounded —structures at Hokuriku areas of Japan. It is found that all the leaders are initiated without any in-cloud discharge activity as their triggers. The average leader speeds we measured are around 106 m/s. All the leaders appear to contain a few pulses soon after their initiations. Pulse rise time ranges from 3.1 μs to 71.4 μs with a GM (Geometric Mean) value of 27.2 μs. Pulse decay time varies from 3.7 μs to 148.8 μs with a GM value of 30.9 μs. Pulse time duration distributes from 12.6 μs to 208.3 μs with a GM value of 59.8 μs. Most of the pulses are the same type of ICC (Initial Continuous Current) pulses. In addition, several correlations such as the light intensity just prior to each pulse versus pulse peak intensity are presented for the pulses.
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Letter
  • Short Time Interval Decay Measurement of Space Charge in Epoxy Resin
    Shinichi Mitsumoto, M. Fu, L. A. Dissado, J. C. Fothergill
    2006 Volume 126 Issue 4 Pages 260-261
    Published: 2006
    Released on J-STAGE: July 01, 2006
    DOIhttps://doi.org/10.1541/ieejfms.126.260
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    It is shown here that positive space charge was formed mainly near the anode when a DC voltage in the range 8 -13kV was applied to a epoxy resin sample for one hour of which thickness is 280μm. When the voltage was removed most of this charge disappeared in a few tens of seconds, but the remainder decayed on a much longer time scale, i.e. there are two types of decay region, a fast decay and a slow decay. Here we investigate the decay mechanism of the space charge in the fast decay region. It was found that the rate of decay in this region was greater when the applied voltage and the amount of injected charge was bigger, and that the decay current estimated from the decay plot obeyed a Schottky relationship with the electrode field estimated from the space charge distribution. Furthemore the relative permittivity calculated from the slope of the Schottky plot was near the known value for the epoxy resin. It is concluded that charge injection via the Schottky mechanism determines the neutralising current in the fast decay region.
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