著者

Mitsuo KEIMATSU Naoshi FUKUSHIMA Takesi NAGATA

出版者

Society of Geomagnetism and Earth, Planetary and Space Sciences

雑誌

Journal of geomagnetism and geoelectricity (ISSN:00221392)

巻号頁・発行日

vol.20, no.1, pp.45-50, 1968-03-20 (Released:2010-09-14)

参考文献数

10

被引用文献数

12 22

---

In order to trace the secular variation of the geomagnetic field in historic time, the documents of ancient aurorae can be utilized. In China, Korea and Japan, there are a number of valuable records, which can be reasonably supposed to describe the events of auroral appearance. After a comparison of these descriptions with those in Europe, the archaeo-secular variation in the geomagnetic field can be inferred. A preliminary examination of the auroral appearance on the same day in the Occident and Orient suggests that the geomagnetic dipole axis might have been inclined towards China around 11-12th centuries AD.

著者

T. Oguti

出版者

Society of Geomagnetism and Earth, Planetary and Space Sciences

雑誌

Journal of geomagnetism and geoelectricity (ISSN:00221392)

巻号頁・発行日

vol.45, no.3, pp.231-242, 1993-03-20 (Released:2007-04-03)

参考文献数

20

被引用文献数

6 6

---

Variations in the location of the auroral zone over the past 1000 years is inferred from a model of secular variation in the geomagnetic field and its backward extrapolation. It is shown that the auroral zone was elongated and deviated towards the European sector 300 years ago, although it is deviated to the Canadian sector at present. The northern UK was located in or very close to the auroral zone, and large parts of the UK, Denmark and northern Germany were in the subauroral zone at that time. It cannot be accidental that the studies of aurorae were developed in France and the UK in the 17th and 18th centuries.

著者

DEUTSCH E. R.

出版者

Society of Geomagnetism and Earth, Planetary and Space Sciences

雑誌

Journal of geomagnetism and geoelectricity (ISSN:00221392)

巻号頁・発行日

vol.8, no.3, pp.108-117, 1956

被引用文献数

3

---

An experimental method is described, designed chiefly to furnish data for a study of the direction, and stability with time, of thermoremanence in rocks. Specimens were heated to the Curie point in an evacuated electric furnace. Two pick-up coils were arranged close to the gap of a tuned a. c. electromagnet providing a maximum field <i>H</i> of 2400 oersteds. These were balanced to make their resultant e. m. f. zero in the presence of <i>H</i> alone, and proportional to <i>dI/dt</i> when a specimen of intensity of magnetization <i>I</i> was in the gap. This e. m. f. was applied to the vertical plates of a cathode ray oscilloscope. The potential drop over a small resistance in the electromagnet input was applied to the deflection coils, giving a measure of <i>H</i>. Computations based on the resulting pattern on the c. r. o. screen yield a loop of the <i>I-H</i> type, with <i>I</i> in arbitrary units, from which the coercivity can be evaluated. A pronounced "sawtooth" pattern has been observed in the (<i>dI/dt)-H</i> traces of pyrrhotite and franklinite specimens, particularly just below the respective Curie points.

著者

Akira HAYASHIDA

出版者

Society of Geomagnetism and Earth, Planetary and Space Sciences

雑誌

Journal of geomagnetism and geoelectricity (ISSN:00221392)

巻号頁・発行日

vol.36, no.12, pp.585-608, 1984 (Released:2010-09-14)

参考文献数

34

被引用文献数

3 3

---

Detailed paleomagnetic studies have been carried out on two sections of the Pleistocene sediments in the Kinki district, central Japan: the Takashima Formation exposed on the northwest coast of Lake Biwa, and the terrace forming deposits distributed in the northern area of Akashi City, about 150km west of Lake Biwa. While these strata are assigned to the late Brunhes normal epoch, reversed polarity zones are observed in both sections. Based on correlation of volcanic ash layers intercalated in the sections, these reversed polarity zones are identified as the records of a reversed polarity episode, the Biwa I ‘event’, which was previously reported from a 200-m-long core sample from Lake Biwa. This result confirms occurrence of a fully reversed geomagnetic field in the late Brunhes Epoch at least in central Japan. The Biwa I episode is possibly correlated to the Jamaica ‘event’ known from several deep-sea cores, and then the episode is suggested to be a global geomagnetic phenomenon in the late Brunhes epoch.

著者

Charles R. DENHAM

出版者

Society of Geomagnetism and Earth, Planetary and Space Sciences

雑誌

Journal of geomagnetism and geoelectricity (ISSN:00221392)

巻号頁・発行日

vol.26, no.5, pp.487-498, 1974 (Released:2010-03-12)

参考文献数

29

被引用文献数

51 61

---

Paleomagnetic directions from two sites at Mono Lake, California, 24000 years ago traced-out a well-defined counter-clockwise loop 25° in diameter. Major features of the loop can be explained by an inward directed radial dipole located at 0.5 Earth's radius, drifting eastward along a path 15° south of Mono Lake. Its longitudinal velocity was 0.10-0.19°/yr and its strength was 0.12-0.21 relative to the Earth's main dipole moment. The life-span of this perturbing source probably was similar to the period of the magnetic loop, about 850 years.

著者

J. Marvin Herndon

出版者

Society of Geomagnetism and Earth, Planetary and Space Sciences

雑誌

Journal of geomagnetism and geoelectricity (ISSN:00221392)

巻号頁・発行日

vol.45, no.5, pp.423-437, 1993-05-20 (Released:2007-04-03)

参考文献数

63

被引用文献数

29 37

---

Ideas have previously been advanced suggesting the possibility that uranium exists within the Earth's core. In. the present paper, evidence is presented for the existence within the Earth's core of substantial quantities of uranium and thorium. The concept of an accumulation of uranium in the core of the Earth functioning as a nuclear fission breeder reactor is presented. Means for concentrating actinide elements within the Earth's core and for separating actinide elements from reactor poisons are disclosed. Nuclear reactor feasibility is demonstrated by Fermi's k∞ in excess of unity for times in the geological past. The concept that the Earth's geomagnetic dynamo is driven by nuclear fission energy is discussed as is the concept that the frequent, but irregular, polarity reversals of the geomagnetic field have their origins in intermittent nuclear reactor output. Although great uncertainty exists in estimates of the abundances of the actinide elements in the core of the Earth and in details of the chemistry of the core, the results of the present paper indicate if uranium and thorium exist in the core of the Earth as elements or compounds, as evidence indicates, the actinides: (1) would be the most dense matter in the Earth; (2) would tend to concentrate at the center of the Earth; (3) would tend to be separated on the basis of density from less dense reactor poisons; and (4) if accumulated 3000 million years ago, would be able to initiate self-sustaining nuclear fission chain reactions which may continue to the present through fuel breeding reactions. The magnitude of available nuclear fission energy release throughout geological time is of major geophysical importance and is more than sufficient to power the geomagnetic field.

著者

M. K. TUNÇER N. OSHIMAN S. BARIS Z. KAMACI M. A. KAYA A. M. ISIKARA Y. HONKURA

出版者

Society of Geomagnetism and Earth, Planetary and Space Sciences

雑誌

Journal of geomagnetism and geoelectricity (ISSN:00221392)

巻号頁・発行日

vol.43, no.11, pp.937-950, 1991 (Released:2010-09-14)

参考文献数

16

被引用文献数

16 16

---

Observations of the geomagnetic total intensity have been carried out from time to time in a possible seismic gap region in the western part of the North Anatolian Fault Zone (NAFZ), in an attempt to trace faultlines through magnetic characteristics and also to relate the characteristics to fault activity. Here we report the results of profile measurements made across the Iznik-Mekece fault as well as our interpretation. The anomalies which we found near Iznik City are similar with the ones that have been found along the eastern part of the Iznik-Mekece fault and hence they could be interpreted in terms of a dike-like structure in the andesite zone adjacent to the fault. In this area the northern edge of the dike-like structure turns out to correspond to the faultline, providing a piece of evidence for the location of faultline. In addition, the dip angle of the dike-like structure provides information on the dip-slip constituent of the primarily right-lateral Iznik-Mekece fault.

著者

S. I. Braginsky

出版者

Society of Geomagnetism and Earth, Planetary and Space Sciences

雑誌

Journal of geomagnetism and geoelectricity (ISSN:00221392)

巻号頁・発行日

vol.45, no.11-12, pp.1517-1538, 1993-12-20 (Released:2011-08-23)

参考文献数

17

被引用文献数

72 91

---

The dynamics of the stably stratified layer at the top of the core, which we call the H-layer or the hidden ocean of the core (HOC), is considered. It is shown that global axisymmetric eigenoscillations of the H-layer are possible that are similar to MAC-waves. These oscillations have periods of the order of a few decades (∼65 yr) if N ∼ 2Ω where N is the Brunt-Väisälä frequency of the H-layer and Ω is the frequency of the Earth's rotation. H-layer oscillations can be excited by an instability mechanism that resembles baroclinic (sloping) instability, and they in turn can excite torsional oscillations (TO) in the bulk of the core. The joint action of these two oscillations provide a mechanism for the generation of the decade geomagnetic secular variations, and the associated variations in the length of day. Rough estimates of the physical parameters of the H-layer are obtained by comparison of the HOC-oscillation theory with observations. The existence of the H-layer has significant consequences for the Earth's dynamo, that are briefly discussed.

著者

R. A. LANGEL T. J. SABAKA R. T. BALDWIN

出版者

Society of Geomagnetism and Earth, Planetary and Space Sciences

雑誌

Journal of geomagnetism and geoelectricity (ISSN:00221392)

巻号頁・発行日

vol.44, no.9, pp.745-767, 1992 (Released:2010-09-14)

参考文献数

17

被引用文献数

4 3

---

All available magnetic data from observatories, satellites, repeat station measurements, and aeromagnetic, shipborne and land surveys are used to derive spherical harmonic models of the geomagnetic field from 1970 to 1990. Two models are derived, one using data from the DE-2 satellite the other not, since the quality of that data is unknown. These models are designated GSFC (11/90) D and GSFC (11/90) respectively. Main field coefficients are determined up to degree 13 and temporal variation, represented by B-splines, up to degree 10. Bias values at the fixed observatories were included as part of the solution. The secular variation models are smoothed by use of norm minimization. Both models fit the data very well.The resulting secular variation shows a jerk-like trend change in several coefficients near 1979.Candidate DGRF 1985 and IGRF 1990 models are extracted from the more general models by projecting to the desired epoch and using a truncated version of the main field spherical harmonic coefficients at those epochs.

著者

Christopher R. SCOTESE Sigmund SNELSON William C. ROSS Linda P. DODGE

出版者

Society of Geomagnetism and Earth, Planetary and Space Sciences

雑誌

Journal of geomagnetism and geoelectricity (ISSN:00221392)

巻号頁・発行日

vol.32, no.Supplement3, pp.SIII61-SIII70, 1980 (Released:2010-03-12)

参考文献数

41

被引用文献数

2 4

---

A computer animation of continental drift has been produced which illustrates the movements of the continents during the last 545 million years. Beginning in the Late Cambrian, the animation shows the sequence of continental collisions which by the end of the Paleozoic formed the supercontinent, Pangaea. The remainder of the film describes the breakup of Pangaea and the subsequent formation of the world's ocean basins. The animation was made at Shell Development Company, Houston, Texas. It is entitled, Dynamic Continents, and is black and white, silent, and runs approximately 5min.

著者

Iwane Kimura

出版者

Society of Geomagnetism and Earth, Planetary and Space Sciences

雑誌

Journal of geomagnetism and geoelectricity (ISSN:00221392)

巻号頁・発行日

vol.39, no.4, pp.175, 1987 (Released:2010-09-14)

著者

S. O. IFEDILI

出版者

Society of Geomagnetism and Earth, Planetary and Space Sciences

雑誌

Journal of geomagnetism and geoelectricity (ISSN:00221392)

巻号頁・発行日

vol.43, no.4, pp.255-266, 1991 (Released:2010-09-14)

参考文献数

66

被引用文献数

4 3

---

The nature of atmospheric neutrons as well as their contributions to the earth's radiation belts are discussed. Our estimates of the trapped proton fluxes from atmospheric neutrons indicate that GRAND, cosmic ray albedo neutron decay, is the major source of protons (E>30MeV) in the radiation belts for L≤1.8. More trapped proton differential energy measurements at L>1.8 are required in order to test the CRAND theory at L>1.8.The CRAND as well as the solar proton albedo neutron decay (SPAND) source is found too weak to supply the large low energy (≤10MeV) inner zone proton intensities.However, the inner zone proton fluxes from our cross-L diffusion calculations are in reasonable agreement with the observed fluxes at energies ≤30MeV. Diffusion inward from the solar wind appears to be the major source of the low energy inner zone protons.

著者

U. S. -Japan Paleomagnetic Cooperation Program in

出版者

Society of Geomagnetism and Earth, Planetary and Space Sciences

雑誌

Journal of geomagnetism and geoelectricity (ISSN:00221392)

巻号頁・発行日

vol.27, no.1, pp.57-66, 1975 (Released:2010-03-12)

参考文献数

23

被引用文献数

13 14

---

A paleomagnetic study of 24 lava flows from Pagan Island (18.1°N, 145.7°E) in the Mariana Islands was conducted to determine the geomagnetic paleosecular variation in the Western Pacific. All flows are normally magnetized, and attempts to obtain radiometric ages for these flows were unsuccessful, and paleointensity determinations by the ‘Thellier method’ were unreliable. The mean virtual geomagnetic pole, (88°N, 110°W) is not significantly different from the rotation axis, suggesting that the lavas erupted over a period that spans at least several thousand years. The between-site angular dispersion SB, is used as a measure of the secular variation. SB=6.0° with respect to the mean VGP, and SB=6.2° with respect to the axis of rotation with a 95 percent confidence interval for the latter of 5.2°<SB<7.8°. Possible interpretations of the data include: (1) the sites studied represent an inadequate coverage in time; (2) the Marianas should be included in the Pacific dipole window; (3) there is a belt of average low angular dispersion encircling the earth between (roughly) 0° and 40°N.

著者

Václav BUCHA

出版者

Society of Geomagnetism and Earth, Planetary and Space Sciences

雑誌

Journal of geomagnetism and geoelectricity (ISSN:00221392)

巻号頁・発行日

vol.32, no.4, pp.217-264, 1980 (Released:2010-03-12)

参考文献数

43

被引用文献数

4 6

---

The correlations between geomagnetic, climatic, and meteorological phenomena were investigated with the object of demonstrating the function of the geomagnetic pole and changes of its position in controlling the climate and weather. A tentative model has been proposed to enable one to understand the causes of the generation of glacial and interglacial periods, as well as the causes which effect changes of climate (BUCHA, 1976a).The analyses of various types of geomagnetic and atmospheric manifestations have disclosed certain associations. The coincidence in the occurrence of increased spectral densities with regard to geomagnetic activity and the variations of atmospheric pressure over the geomagnetic pole shows the relation between their periodicities. The results imply that the changes in the intensity of corpuscular radiation, indicated by geomagnetic activity, affect the temperature and pressure patterns over the geomagnetic pole and polar region significantly, so that a pronounced modification of the general circulation may take place, as shown schematically (BUCHA, 1976b).As a result of investigating the relations between the variations of geomagnetic activity and meteorological factors a mechanism of solar-terrestrial relationships and a model of the changes of atmospheric circulation in the Northern Hemisphere are proposed; this provides a probable explanation of the causes of the fluctuation of the climate, of dry and cold periods and of differing vegetation conditions in various years in dependence on the intensity of geomagnetic activity (BUCHA, 1976b, 1977a).

著者

MUKHERJEE G. K. RAJARAM Ramaswamy

出版者

地球電磁気・地球惑星圏学会

雑誌

Journal of geomagnetism and geoelectricity (ISSN:00221392)

巻号頁・発行日

vol.34, no.11, pp.619-632, 1982

被引用文献数

1

---

The seasonal variations of the plasma dynamics have been investigated using Mead-Fairfield model. It is shown that shifts in the mirror points and meridional drifts are introduced as a result of the season dependent tilt of the dipole axis with the earth-sun line. Other parameters like radial and azimuthal drifts and the bounce periods are free from seasonal variations. The maximum shift in the mirror points and latitudinal drifts are produced in particles bouncing close to the equator but the former peaks in the mid-night meridian while the latter maximises (in magnitude) in the dawn and dusk sectors. A theoretical estimate has been obtained for the seasonal geomagnetic variation associated with these distortions of the ring current. It is shown that the seasonal variations in the declination can be accounted for if the ring current radius is taken as 7 earth radii.

著者

E. DAWSON L. R. NEWITT

出版者

Society of Geomagnetism and Earth, Planetary and Space Sciences

雑誌

Journal of geomagnetism and geoelectricity (ISSN:00221392)

巻号頁・発行日

vol.34, no.4, pp.225-240, 1982 (Released:2010-03-12)

参考文献数

36

被引用文献数

9 14

---

The motions of the Earth's magnetic dip poles and geomagnetic poles over the past 400 years are investigated. In addition, relations are sought between geomagnetic and virtual geomagnetic poles over historic times.Since 1750, the secular motion of the dip poles along their paths has been counterclockwise. During this century this secular motion has been directed in a northwest direction with an average velocity of -11km per year for the north dip pole and -10km per year for the south dip pole. In 1980, the north dip pole was located at 77.3°N and 101.8°W in the Canadian Archipelago, and the south dip pole at 65.6°S and 139.4°E just off mainland Antarctica.In addition to its secular motion, each dip pole undergoes a diurnal motion caused by ionospheric current systems. This motion, which is clockwise in the north and anticlockwise in the south, may result in a displacement from the unperturbed position of 65km and 30km respectively, on an average disturbed day.The average velocity of the north geomagnetic pole during this century is -1km per year in a northwest direction. It is about a magnitude less for the virtual geomagnetic pole. Both the geomagnetic and virtual geomagnetic pole paths display a clockwise rotation.There is a great deal of uncertainty in our attempt to use virtual geomagnetic poles to extend the geomagnetic pole path back in time to -7500 B. C. Much of this uncertainty is due to the sparse distribution of archeomagnetic measurements at a given epoch.

著者

OGAWA Toshio TANAKA Yoshikazu MIURA Teruo YASUHARA Michihiro

出版者

地球電磁気・地球惑星圏学会

雑誌

Journal of geomagnetism and geoelectricity (ISSN:00221392)

巻号頁・発行日

vol.18, no.4, pp.443-454, 1966

被引用文献数

69

---

A simple observing system for the measurements of vertical electric field component of natural ELF and VLF electromagnetic noises by using ball antennas is described. With this system it is possible to measure long traveled natural ELF noises discriminated from natural local noises due to such as atmospheric electric space-charge fluctuations. Some of the typical recorded noises are shown. Observed ELF noises are divided into three characteristic types; &ldquo;ELF flash&rdquo;, &ldquo;ELF burst&rdquo; (N-and Q-types), and &ldquo;ELF continuous&rdquo;. ELF flashes originate from the lightning discharges in the area within about 1, 000km from the observing station. Occurrences of ELF bursts are more frequent in the daytime than in the nighttime, and are characterized by sudden increase at the time of local sunrise, suggesting the related mechanism of their generation to the solar position relative to the earth. N-type bursts are followed by VLF noises. Source distances of these bursts which are followed by tweek-type atmospherics in the night are estimated to be in the range from 2, 500km to 5, 000km. Q-type bursts often show clear oscillations of the frequencies of Schumann resonances. The daily variations of the mean amplitude of &ldquo;ELF continuous&rdquo; which composes the background noises are quite similar to the daily variations of the world thunderstorm activity.

著者

J. M. A. Miranda M. A. Pais I. P. Abreu

出版者

Society of Geomagnetism and Earth, Planetary and Space Sciences

雑誌

Journal of geomagnetism and geoelectricity (ISSN:00221392)

巻号頁・発行日

vol.49, no.2-3, pp.373-386, 1997-02-20 (Released:2011-08-23)

参考文献数

15

被引用文献数

1 2

---

The aim of this study is to analyse the integration of sparse three component magnetic observations from observatories and repeat stations with dense total field values from aeromagnetic data, into a homogeneous description of the magnetic field. The methodology followed implies the independent computation of main and crustal field contributions, each one incorporating the constraints of harmonicity. The crustal anomalous field is calculated for 1980 by digital filtering of the total field values from aeromagnetic surveys; the convolution is made in the spatial domain with space varying coefficient sets to account for the change in direction of the main field. The main field is estimated by updating the DGRF80, whose agreement with the Iberian data has already been demonstrated, with a SCHA model for the secular variation deduced from 360 three component observations over the Iberian Peninsula for the period 1980-1991. The combination of these two contributions permits one to compute magnetic component maps for the 1991.0 epoch that agree, in the least-squares sense, with the observational data while respecting the mathematical characteristics of a potential field. This methodology seems to be an effective way to produce regional estimations of the internal field.

著者

K. Mohanakhmar

出版者

Society of Geomagnetism and Earth, Planetary and Space Sciences

雑誌

Journal of geomagnetism and geoelectricity (ISSN:00221392)

巻号頁・発行日

vol.48, no.3, pp.343-352, 1996-03-20 (Released:2007-05-25)

参考文献数

17

被引用文献数

1 3

---

A study on the influence of solar activity and phases of equatorial quasi-biennial oscillation (QBO) on tropical rainfall over India has been made. The results of the total rainfall over the country indicate that during the period of low solar activity, excess/normal rainfall (frequent floods) are associated with the westerly phase of QBO and deficient/normal rainfall (frequent droughts) corresponded to the easterly phase. During the period of high solar activity only normal rain is observed when QBO is in its westerly phase. Multiple regression analysis has employed to estimate the summer monsoon rainfall using sunspot number and equatorial zonal wind at 15-20 hPa during January-February as independent parameters. A study on the spatial variability of monsoon rainfall in response to the solar activity and phases of QBO has also been attempted.

著者

C. Agodi ONWUMECHILI

出版者

Society of Geomagnetism and Earth, Planetary and Space Sciences

雑誌

Journal of geomagnetism and geoelectricity (ISSN:00221392)

巻号頁・発行日

vol.44, no.1, pp.1-42, 1992 (Released:2010-09-14)

参考文献数

62

被引用文献数

17 22

---

A review of indications of the return currents of the equatorial electrojet (EEJ) and associated phenomena has been presented. The need for good fitting of the observed dip equatorial magnetic variation profiles had compelled the inclusion of westward currents on the flanks of the dip equator in practically all the cases. The three sources of the return currents: the curvature of the field lines through the ionospheric dynamo region, the divergence of east-west currents close to the magnetic dip equator, and the local neutral winds varying with height combine constructively, each peaking around 5° dip latitude, to provide for the return currents of practically all the eastward electrojet current. The return currents flow on the flanks of the dip equator from about 3° and terminate at a dip distance L1 in the interval 7°≤L1≤17° with a mean of L1=10±3°, sometimes extending further but not beyond the Sq focus. At a location about 5.2±0.8° dip latitude, they reach a peak of about -27±3 per cent of the peak of the eastward equatorial electrojet. The negative correlation between the width and the intensity of the equatorial electrojet has been confirmed with data derived from physical model, indicating its origin in the westward return currents. The ionospheric current system so far detected by rockets is essentially in two layers. It is suggested that the intense lower layer including the return currents around 5° dip latitude, be associated with the equatorial electrojet; and that the weak upper layer that maintains more steady altitude extent everywhere be associated with the worldwide part of the Sq currents.