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Equatorial counter-electrojet and magnetic pulsations 赤道反电喷流和磁脉动
Journal of geomagnetism and geoelectricity Pub Date : 1997-10-20 DOI: 10.5636/JGG.49.1247
T. Sastry, S. Sarma
{"title":"Equatorial counter-electrojet and magnetic pulsations","authors":"T. Sastry, S. Sarma","doi":"10.5636/JGG.49.1247","DOIUrl":"https://doi.org/10.5636/JGG.49.1247","url":null,"abstract":"The signal amplitudes in the Hx component of magnetic pulsations undergo significant enhancement at the dip equator during intervals of Equatorial Electrojet (EEJ), the enhancement attaining a peak value during prenoon hours. On the other hand, it is shown in this study, that the enhancement peak which occurs during prenoon hours on EEJ days shifts towards noon hours on major counter electrojet (CEJ) days. The observed shift of the peak towards noon hours is interpreted to indicate corresponding change in the diurnal variation of ionospheric conductivity during the CEJ days.","PeriodicalId":156587,"journal":{"name":"Journal of geomagnetism and geoelectricity","volume":"10 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1997-10-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123379263","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Magnetospheric ULF Wave Phenomena Stimulated by SSC SSC激发的磁层超低频波现象
Journal of geomagnetism and geoelectricity Pub Date : 1997-10-20 DOI: 10.5636/JGG.49.1179
K. Yumoto, V. Pilipenko, E. Fedorov, N. A. Kurneva, M. Lauretis, K. Kitamura
{"title":"Magnetospheric ULF Wave Phenomena Stimulated by SSC","authors":"K. Yumoto, V. Pilipenko, E. Fedorov, N. A. Kurneva, M. Lauretis, K. Kitamura","doi":"10.5636/JGG.49.1179","DOIUrl":"https://doi.org/10.5636/JGG.49.1179","url":null,"abstract":"Several ssc were recorded simultaneously at the low-latitude longitudinal and along the 210° magnetic meridian networks. The considered ULF wave phenomena stimulated by the ssc comprise main and preliminary impulses, Psc 3 pulsations, ssc-related Pc 3 and cavity-like oscillations. The analysis of observed ssc shows that the preliminary impulse is still not able to explain invoking by the existing theory. It is also found some problems concerning the interpretation of features of other ssc-associated wave phenomena. Further specially coordinated observations at a world-wide magnetometer network with high precision of time synchronization are required to understand these unresolved problems.","PeriodicalId":156587,"journal":{"name":"Journal of geomagnetism and geoelectricity","volume":"7 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1997-10-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122033417","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 17
Remagnetization of the Pyeongan Supergroup in the Yeongwol Area, Korea 韩国盈月地区平安超级群的再磁化
Journal of geomagnetism and geoelectricity Pub Date : 1997-10-20 DOI: 10.5636/JGG.49.1217
S. Doh, D. Suk, Yong-Hee Park
{"title":"Remagnetization of the Pyeongan Supergroup in the Yeongwol Area, Korea","authors":"S. Doh, D. Suk, Yong-Hee Park","doi":"10.5636/JGG.49.1217","DOIUrl":"https://doi.org/10.5636/JGG.49.1217","url":null,"abstract":"Paleomagnetic and rock magnetic investigations have been carried out for the late Carboniferous-Permian Pyeongan Supergroup, exposed in the Yeongwol area in eastern South Korea. A total of 228 independently oriented core samples was drilled from thirteen sites for the study. The mean direction after bedding correction (D/1 = 202.7°/-24.6°, k = 2.4, cm 5 = 36.9°) is more dispersed than the in-situ mean direction (D/I = 175.3°/-58.9°, k = 69.0, cm 5 = 5.3°), indicating that the fold test is negative at 95% confidence level. In addition, the stepwise unfolding of the characteristic remanent magnetization (ChRM) reveals a maximum value of at 0% unfolding. Furthermore, authigenic magnetite and hematite grains are identified by the electron microscope observations. These results collectively imply that the ChRM directions were acquired after tilting of the strata by a chemical remanent magnetization when the secondary authigenic magnetic minerals formed. The ChRM directions of the Supergroup, however, pass the reversal test at 95% confidence level suggesting that the remagnetization occurred during the period including both normal and reversed polarity intervals. Because the paleomagnetic pole position (39.4°E, 85.6°N, A 95 = 8.9°) of the Pyeongan Supergroup calculated from the mean site directions of the ChRMs is close to that of the Tertiary period of the Korean Peninsula, it is interpreted that the remagnetization in this area occurred during the Tertiary. However, it is also plausible that the study area might be rotated about 30° anticlockwise after the remagnetization at the end of the Daebo Orogeny, in the beginning of the Cretaceous period.","PeriodicalId":156587,"journal":{"name":"Journal of geomagnetism and geoelectricity","volume":"66 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1997-10-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114836499","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 9
Confidence Limit for the Existence of a Solution to the One-Dimensional Magnetotelluric Inverse Problem 一维大地电磁反演问题解存在性的置信限
Journal of geomagnetism and geoelectricity Pub Date : 1997-09-20 DOI: 10.5636/JGG.49.1145
Yuanchou Zhang, K. Paulson
{"title":"Confidence Limit for the Existence of a Solution to the One-Dimensional Magnetotelluric Inverse Problem","authors":"Yuanchou Zhang, K. Paulson","doi":"10.5636/JGG.49.1145","DOIUrl":"https://doi.org/10.5636/JGG.49.1145","url":null,"abstract":"The necessary and sufficient conditions for the existence of a solution to the one-dimensional magnetotelluric inverse problem are extended to error data. The confidence criterion is defined and used for testing the existence of a one-dimensional solution when data errors are considered. Synthetic data sets and two very popular real data sets are tested using this new confidence criterion.","PeriodicalId":156587,"journal":{"name":"Journal of geomagnetism and geoelectricity","volume":"249 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1997-09-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115230203","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
A possible signature of magnetic cavity mode oscillations in ISEE spacecraft observations ISEE航天器观测中磁腔模式振荡的可能特征
Journal of geomagnetism and geoelectricity Pub Date : 1997-09-20 DOI: 10.5636/JGG.49.1079
M. Kivelson, M. Cao, R. McPherron, R. Walker
{"title":"A possible signature of magnetic cavity mode oscillations in ISEE spacecraft observations","authors":"M. Kivelson, M. Cao, R. McPherron, R. Walker","doi":"10.5636/JGG.49.1079","DOIUrl":"https://doi.org/10.5636/JGG.49.1079","url":null,"abstract":"The structure of magnetohydrodynamic waves in the terrestrial magnetosphere is controlled by the dispersion relations of the wave modes, the inhomogeneities of the system and the boundary conditions. If the waves are confined within the magnetospheric cavity with proper boundary conditions, two types of spectra are predicted by MHD theory. One is a discrete compressional spectrum and the other is a continuous shear Alfven spectrum. The discrete spectrum refers to compressional eigenmodes with spatially constant eigenfrequencies. The continuous shear Alfven spectrum corresponds to field line resonances with spatially varying resonant frequencies. There have been many reports of observations consistent with the theoretical predictions for shear Alfven waves. However, only a few spacecraft observations of the global cavity eigenmodes or the coupling between the two modes have been reported. Here we report an observation using ISEE 1 and 2 spacecraft magnetometer data. On a quiet day with low solar wind dynamic pressure and low geomagnetic activity, the ISEE 1 and 2 spacecraft identified a compressional wave with constant frequency throughout most of its inbound orbit in the outer magnetosphere. Multiple harmonics of shear Alfven waves with spatially varying frequencies were observed in the azimuthal component. Evidence of the coupling between these two waves in found. Comparing our observations with the results of a computer simulation in a dipole field, we find qualitative (not quantitative) agreement. We also consider why so few examples of radially-extended monochromatic compressional oscillations have been found. We conclude that the exceptional circumstances required for development and identification of these wave structures occur very rarely.","PeriodicalId":156587,"journal":{"name":"Journal of geomagnetism and geoelectricity","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1997-09-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130111970","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 23
Propagation of Solar Neutron-Decay Protons near the Earth 太阳中子衰变质子在地球附近的传播
Journal of geomagnetism and geoelectricity Pub Date : 1997-09-20 DOI: 10.5636/JGG.49.1105
T. Sakai, M. Kato, Y. Muraki
{"title":"Propagation of Solar Neutron-Decay Protons near the Earth","authors":"T. Sakai, M. Kato, Y. Muraki","doi":"10.5636/JGG.49.1105","DOIUrl":"https://doi.org/10.5636/JGG.49.1105","url":null,"abstract":"A Monte Carlo simulation of solar neutron-decay protons is performed using a simple interplanetary magnetic field (slab model) in interplanetary space. The time profile of solar neutron-decay protons obtained by our simulation is compared with observations. It is shown that the simple model can predict coherent pulses at the start of events. Magnetic field parameters used in the comparison can suggest the mean free path of protons near the Earth. The values are discussed in relation to other published results. Also, the comparisons show that it is difficult to determine the angular distribution of solar neutrons emitted at a flare site as long as the presently available solar neutron-decay protons are used.","PeriodicalId":156587,"journal":{"name":"Journal of geomagnetism and geoelectricity","volume":"12 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1997-09-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123190961","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 1
Plasma Acceleration in the Magnetotail as an Origin of the Electric Field Generation during a Substorm 磁尾中的等离子体加速是次暴期间电场产生的一个来源
Journal of geomagnetism and geoelectricity Pub Date : 1997-09-20 DOI: 10.5636/JGG.49.1099
A. Podgorny, I. Podgorny, S. Minami
{"title":"Plasma Acceleration in the Magnetotail as an Origin of the Electric Field Generation during a Substorm","authors":"A. Podgorny, I. Podgorny, S. Minami","doi":"10.5636/JGG.49.1099","DOIUrl":"https://doi.org/10.5636/JGG.49.1099","url":null,"abstract":"Field-aligned currents and westward electrojet enhancement are produced by electric field generation in the magnetotail during a substorm. The space measurements during the substorm and laboratory experiments support the model of earthward electric field production in the magnetotail current sheet. The results of numerical MHD simulation are presented. The quasistationary current sheet is created at plasma jet injection in the perpendicular magnetic field. The current sheet becomes unstable after plasma injection is ceased, and the local plasma velocity along the sheet drops to zero. The instability development produces fast current density enhancement and plasma acceleration by j×B/c force. In such conditions the Earthward j×B/nec electric field should appear.","PeriodicalId":156587,"journal":{"name":"Journal of geomagnetism and geoelectricity","volume":"70 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1997-09-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133256984","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 3
Observations and Modelling of Nocturnal Ionospheric Irregularities in Low Latitude Region 低纬度地区夜间电离层不规则性的观测与模拟
Journal of geomagnetism and geoelectricity Pub Date : 1997-09-20 DOI: 10.5636/JGG.49.1115
Ashutosh Kumar Singh, R. Singh
{"title":"Observations and Modelling of Nocturnal Ionospheric Irregularities in Low Latitude Region","authors":"Ashutosh Kumar Singh, R. Singh","doi":"10.5636/JGG.49.1115","DOIUrl":"https://doi.org/10.5636/JGG.49.1115","url":null,"abstract":"The analysis of VHF scintillation recorded at Varanasi shows that the ionospheric irregularities over Varanasi are mostly of small duration <30 minutes and are frequently observed during pre-midnight periods. During magnetically disturbed days there is a marked reduction in the occurrence rate of scintillations. The increase of solar activity generally-increases the depth of scintillation. Auto-correlation functions and power spectra of scintillations predict that the mean spectral index is ∼4, and the size of the overhead ionospheric irregularities varies from 200-500 m having drift velocity between 75 m/sec to 200 nl/sec. Drift velocities and spectral indices of ionospheric irregularities derived by us agree well with the results obtained by other workers. It is shown that the thin phase screen model valid for weak scattering could explain the observed features of scintillation. The scintillation index S4, strength of turbulence Cs and its dependence on various parameters are studied and it is found that the S4 index increases with increase in spectral index and decreases with increase in outer scale length Lo.","PeriodicalId":156587,"journal":{"name":"Journal of geomagnetism and geoelectricity","volume":"416 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1997-09-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130564326","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 12
Nature of Electromagnetic Emission Precursory to an Earthquake 地震电磁发射前兆的性质
Journal of geomagnetism and geoelectricity Pub Date : 1997-09-20 DOI: 10.5636/JGG.49.1153
T. Rikitake
{"title":"Nature of Electromagnetic Emission Precursory to an Earthquake","authors":"T. Rikitake","doi":"10.5636/JGG.49.1153","DOIUrl":"https://doi.org/10.5636/JGG.49.1153","url":null,"abstract":"More than 60 occurrences of electromagnetic emission data in Japan precursory to an earthquake are analyzed. It turns out that the larger the main shock magnitude (M), the larger the detectable distance (Dmax) of signal from the epicenter. The M-Dmax relation agrees with that of other geophysical precursors. No dependence of precursor time (T) on M is observed. The situation is much the same as foreshock precursor. The mean precursor time of electromagnetic radiation precursor amounts to 0.26 day, so that the precursor is essentially a short-term one.","PeriodicalId":156587,"journal":{"name":"Journal of geomagnetism and geoelectricity","volume":"48 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1997-09-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116139479","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 21
Geomagnetic Secular Variation at the Indian Observatories 印度天文台地磁的长期变化
Journal of geomagnetism and geoelectricity Pub Date : 1997-09-20 DOI: 10.5636/JGG.49.1131
S. Bhardwaj, G. Rangarajan
{"title":"Geomagnetic Secular Variation at the Indian Observatories","authors":"S. Bhardwaj, G. Rangarajan","doi":"10.5636/JGG.49.1131","DOIUrl":"https://doi.org/10.5636/JGG.49.1131","url":null,"abstract":"Annual mean values of geomagnetic field components D, H and Z for all days and quiet days at six observatories are analysed to investigate the secular variations and geomagnetic jerks in the Indian region. Secular trends show a region of demarkation between equatorial and low latitude stations. The residual D, H and Z curves, obtained by removing polynomial fits, do not show any parallelism with the Il-year sunspot cycle. However, the D residual has a periodicity of 2 solar cycles, whereas H and Z residuals indicate a quasi-periodicity of 3 solar cycles at Alibag. For the period 1958 to 1990, D and Z residuals show a periodicity of nearly 2 solar cycles, while H shows out-of-phase variations with the sunspot cycle for all the six stations. The secular jerk around 1969-70, noted at many observatories over the globe, is not seen in D but is noted in the H and Z components at some of the six Indian stations. A comparison between the observed annual means and IGRF models indicates very low secular variation anomaly in the Indian region.","PeriodicalId":156587,"journal":{"name":"Journal of geomagnetism and geoelectricity","volume":"219 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1997-09-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116243815","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 9
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