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Volume 37, Issue 12
Displaying 1-9 of 9 articles from this issue
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R. P. KANE, N. B. TRIVEDI1985 Volume 37 Issue 12 Pages 1071-1085
Published: 1985
Released on J-STAGE: September 14, 2010
JOURNAL FREE ACCESSThe annual mean sunspot numbers during 1749-1971, are subjected to power spectrum analysis by the recentmost Least-Squares linear prediction method evolved by Barrodale and Erickson. For the two consecutive intervals 1749-1844 and 1845-1971, only one major peak at T=9.7yr is common and many other peaks are different, indicating either unreliability of the earlier data, or a possibility that the two samples do not belong to the same population. In general, peaks near T=5yr have only border-line significance, peaks near T=11yr are highly significant and multiple and probably change with time. In the large periodicity region peaks definitely exist for T=60-100yr range, but probably change with time. Attempts at prediction of future activity yielded a number less than 100 for cycle 21, much lesser than the observed value of 155 in 1979-1980.View full abstractDownload PDF (1491K) -
[I] Winter EnhancementY. IWASAKA, T. HIRASAWA, H. FUKUNISHI1985 Volume 37 Issue 12 Pages 1087-1095
Published: 1985
Released on J-STAGE: September 14, 2010
JOURNAL FREE ACCESSThe measurements on polar stratospheric aerosol particles using lidar and meteorological sonde at Syowa Station (69°00′S, 39°35′E), Antarctica revealed that the content of stratospheric aerosols noticeably increased in winter when atmospheric temperature frequently fell down to about -80°C in the lower atmosphere, and that the depolarization ratio of the backscattered light from the enhanced stratospheric aerosols also has very large value (at least larger than 0.5 during the fully developed enhancement period).View full abstractDownload PDF (728K) -
A Case Study on a B. C. Hydro 500kV Power LineS. LUNDBY, B. E. CHAPEL, D. H. BOTELER, T. WATANABE, R. E. HORITA1985 Volume 37 Issue 12 Pages 1097-1114
Published: 1985
Released on J-STAGE: September 14, 2010
JOURNAL FREE ACCESSTwo empirical formulas were derived which jointly make it possible to predict size of GIC (geomagnetically induced current) in a power line as a function of Kp, a three-hourly planetary magnetic activity index. GIC size is represented by an hourly-range value, i. e., the difference between the maximum and minimum GIC values for a time interval of an hour. The formulas are based on the data obtained from a 500kV power line of B. C. Hydro which extends 400km long in an east-west direction at a geomagnetic latitude of about 60°. One of the two formulas relates mean GIC size with Kp; it was found that, on the average, GIC size changes exponentially with Kp. The other formula describes the scatter of individual values of GIC size about the average trend described by the first formula. The scatter was found to follow a lognormal distribution. The parameters in these formulas were determined from two groups of data: one includes the entire available data and the other covers data for 1+≤Kp≤50. The data outside this Kp range were scanty. The probability that GIC size exceeds 100 Amperes at Kp=9 is estimated to be 3% and 12%, respectively, based on the two data groups.View full abstractDownload PDF (1379K) -
S. C. WEBB, S. C. CONSTABLE, C. S. COX, T. K. DEATON1985 Volume 37 Issue 12 Pages 1115-1129
Published: 1985
Released on J-STAGE: September 14, 2010
JOURNAL FREE ACCESSA seafloor instrument has been constructed to measure a horizontal component of the electric field, using a long antenna (up to 1000m) to increase sensitivity. The instrument has a depth capability of 5200m and may be deployed for several months at a time, collecting over 14 Mbytes of data under the control of a microprocessor. Instrumental noise is mainly caused by the Ag-AgCl electrodes used to make contact with the sea water, and is about 10-24V2/m2Hz at frequencies above 1Hz, following an f-2 power law at frequencies (f) below 1Hz. For controlled source signals averaging techniques such as synchronous stacking and block averaging have been used to detect narrow band (5.6×10-4Hz) signals as small as 10-12V/m. The instrument is designed to include the pressure transducer described by COX et al. (1984) and has already been used for the study of ocean bottom seismic signals, magnetotelluric experiments and controlled source electromagnetic soundings.View full abstractDownload PDF (5416K) -
Nobuhiro ISEZAKI, Hiroo INOKUCHI1985 Volume 37 Issue 12 Pages 1131-1140
Published: 1985
Released on J-STAGE: September 14, 2010
JOURNAL FREE ACCESSThree-dimensional topographic bodies are approximated more precisely by polygonal pyramids than either by polygonal laminas or by polygonal prisms. Exact forms of indefinite integrals for magnetic anomalies are obtained for a polygonal pyramid whose sides of top and bottom planes are parallel. Magnetic anomalies calculated for such a polygonal pyramid by both polygonal laminas and polygonal prisms show that the large differences from the exact solution occurred in particular at the flank of the polygonal pyramid. It implies that the large number of laminas or prisms are needed to approximate the polygonal pyramid especially when the magnetic observations are made near the magnetic sources. Thus, if the source body can be approximated by a few polygonal pyramids computation time is much less than in other methods.View full abstractDownload PDF (688K) -
Joachim MEYER, Jörn-Henning HUFEN, Manfred SIEBERT, Albrecht HAHN1985 Volume 37 Issue 12 Pages 1141-1145
Published: 1985
Released on J-STAGE: September 14, 2010
JOURNAL FREE ACCESSThis paper deals with the secular change of the induced crustal magnetic field, inferred from a global model of crustal susceptibility distribution and the inducing core field of IGRF 1965 and IGRF 1980. The difference between the spatial spectra of the calculated crustal model fields in the two epochs gives an estimate of the crustal part in the geomagnetic secular variation. Its distribution is approximately uniform over a wide range of spherical harmonic degrees. Thus the spatial spectrum of the secular variation to be observed at the Earth's surface should consist—like that of the internal field itself—of a linearly decreasing core field part and a quasi-white part of crustal origin. The transition from the core to the crustal section appears at the degree of about 16.View full abstractDownload PDF (558K) -
Y. HONKURA, M. SHIMIZU1985 Volume 37 Issue 12 Pages 1147-1155
Published: 1985
Released on J-STAGE: September 14, 2010
JOURNAL FREE ACCESSDownload PDF (720K) -
IAGA DIVISION I WORKING GROUP 11985 Volume 37 Issue 12 Pages 1157-1163
Published: 1985
Released on J-STAGE: September 14, 2010
JOURNAL FREE ACCESSDownload PDF (435K) -
T. Yukutake1985 Volume 37 Issue 12 Pages 1165-1167
Published: 1985
Released on J-STAGE: August 11, 2011
JOURNAL FREE ACCESSDownload PDF (268K)
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