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Magnetic Hysteresis Properties of Fine Particles of Monoclinic Pyrrhotite Fe7S8. 单斜磁黄铁矿Fe7S8细粒磁滞特性
Journal of geomagnetism and geoelectricity Pub Date : 1997-07-20 DOI: 10.5636/JGG.49.965
A. Menyeh, W. O'reilly
{"title":"Magnetic Hysteresis Properties of Fine Particles of Monoclinic Pyrrhotite Fe7S8.","authors":"A. Menyeh, W. O'reilly","doi":"10.5636/JGG.49.965","DOIUrl":"https://doi.org/10.5636/JGG.49.965","url":null,"abstract":"The magnetic hysteresis properties have been studied of synthetic Fe7S8 separated into a suite of 8 particle size fractions in the range 1 to 30μm. Between-196°C to about 260°C, both saturation isothermal remanence (Mrs) and coercive force (Hc) can be represented as analytical functions of particle size (L) of the form (Mrs, Hc) ∝ L-n or (Mrs, Hc) ∝ exp(-kL1+2) although the particle size dependence of Mrs is much weaker than that of Hc. The parameters n and k show a small but systematic fall in values as temperature rises, but may be acceptably constant to furnish analytic functions for physical models of more complex magnetic properties such as thermoremanent magnetization or domain dynamics. The temperature dependence of Hc below room temperature is weaker than that above, possibly due to an increasing single-ion contribution to magnetocrystalline anisotropy. The inferred temperature dependence of magnetocrystalline anisotropy above room temperature up to about 250°C suggests that temperature-induced expulsion or nucleation of domain walls is not expected in this temperature range. The temperature dependence of Mrs and Hc can be expressed as (1 - T/Tc)q where q shows a small but systematic fall as particle size increases in the range 1-30μm. The several properties of the finest, monodomain, fraction (","PeriodicalId":156587,"journal":{"name":"Journal of geomagnetism and geoelectricity","volume":"36 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1997-07-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116854134","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: 7
Ionospheric Elementary Current Systems in Spherical Coordinates and Their Application 球坐标下电离层初等电流系统及其应用
Journal of geomagnetism and geoelectricity Pub Date : 1997-07-20 DOI: 10.5636/JGG.49.947
O. Amm
{"title":"Ionospheric Elementary Current Systems in Spherical Coordinates and Their Application","authors":"O. Amm","doi":"10.5636/JGG.49.947","DOIUrl":"https://doi.org/10.5636/JGG.49.947","url":null,"abstract":"Two sets of basis functions in spherical coordinates are presented, in terms of which any given ionospheric current system, consisting of horizontal sheet currents and their accompanying field-aligned currents, can be expanded, regardless of any considerations on the ionospheric conductances or the electric field. The single basis functions are called elementary current systems. One basis function set is curl-free and poloidal, and causes a toroidal magnetic field that is restricted to the area above the ionosphere. The other one is divergence-free and toroidal, and causes a poloidal magnetic field which is solely responsible for the magnetic effect of ionospheric currents below the ionosphere. The field-aligned currents are assumed to flow radially. The expansion presented is used on a model of a Cowling channel to decompose its Hall and Pedersen currents into their total divergence-free and curl-free parts. This application example shows how the analysis technique based on the elementary current expansion resolves the physically relevant primary and secondary currents inside the Cowling channel.","PeriodicalId":156587,"journal":{"name":"Journal of geomagnetism and geoelectricity","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1997-07-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123182503","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: 193
Numerical Study on Dynamics and Polarization of the Hot Plasma Torus in the Magnetosphere : Cause of Generation of the Paired Region 1 and Region 2 Field-Aligned Currents 磁层热等离子体环面动力学和极化的数值研究:配对区1和区2场向电流产生的原因
Journal of geomagnetism and geoelectricity Pub Date : 1997-07-20 DOI: 10.5636/JGG.49.879
Takashi Yamamoto, S. Inoue, C. Meng
{"title":"Numerical Study on Dynamics and Polarization of the Hot Plasma Torus in the Magnetosphere : Cause of Generation of the Paired Region 1 and Region 2 Field-Aligned Currents","authors":"Takashi Yamamoto, S. Inoue, C. Meng","doi":"10.5636/JGG.49.879","DOIUrl":"https://doi.org/10.5636/JGG.49.879","url":null,"abstract":"To begin with, we postulate that in the magnetosphere, the hot (≥1 keV) plasma particles are primarily distributed in a magnetic shell which is connected to two ovals of diffuse auroras on the northern and southern polar ionospheres. Such hot plasma population is called the hot plasma torus (HPT). To study dynamics and polarization of the HPT in the magnetosphere, we perform the two-dimensional numerical simulations which is capable of treating the electrostatic coupling between the magnetosphere and the ionosphere. The simulation results show that distortion of the HPT occurs due to the solar wind convection when the interplanetary magnetic field (IMF) is southward, so that the polarization of the distorted HPT produces a pair of the region and region 2 field-aligned currents (FACs) which agrees with the observations. It is also shown that the self-distortion of the HPT (positive feedback) is possible; namely, the HPT is further polarized by electric fields arising from the polarized HPT, which leads to intensification of the region 1/region 2 FACs. Notably, in our model the disruption of a tail current is a natural result of the HPT distortion on the nightside, which can explain the observations that the tail current disruption occurs over a wide MLT range and well inside the magnetically closed region.","PeriodicalId":156587,"journal":{"name":"Journal of geomagnetism and geoelectricity","volume":"48 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1997-07-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129364400","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: 2
On the Resolution of the Darai Limestones by Two-Dimensional MT Forward Modeling 基于二维MT正演模拟的大理灰岩分辨率研究
Journal of geomagnetism and geoelectricity Pub Date : 1997-06-20 DOI: 10.5636/JGG.49.817
J. Pous, J. Ledo, Á. Marcuello, P. Queralt
{"title":"On the Resolution of the Darai Limestones by Two-Dimensional MT Forward Modeling","authors":"J. Pous, J. Ledo, Á. Marcuello, P. Queralt","doi":"10.5636/JGG.49.817","DOIUrl":"https://doi.org/10.5636/JGG.49.817","url":null,"abstract":"The PNG data have been analysed to determine the presence of the lower Darai limestones. As a first step, Groom and Bailey decomposition method was applied, which indicated that the electrical structure was approximately two-dimensional and striking N120°. Accordingly, two-dimensional forward modeling of the rotated data was performed. The final model showed the resistivity distribution with alternating resistive Darai limestones and conductive Ieru stratigraphic units. In particular, the model exhibited the resistive lower Darai limestones along the whole profile, which was the question posed at the MT-DIW2. A sensitivity test was performed to ensure the presence of the lower Darai limestones was resolvable.","PeriodicalId":156587,"journal":{"name":"Journal of geomagnetism and geoelectricity","volume":"5 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1997-06-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124064361","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: 6
Introduction to MT-DIW2 Special Issue MT-DIW2特刊简介
Journal of geomagnetism and geoelectricity Pub Date : 1997-06-20 DOI: 10.5636/JGG.49.727
A. Jones, Adam Schultz
{"title":"Introduction to MT-DIW2 Special Issue","authors":"A. Jones, Adam Schultz","doi":"10.5636/JGG.49.727","DOIUrl":"https://doi.org/10.5636/JGG.49.727","url":null,"abstract":"","PeriodicalId":156587,"journal":{"name":"Journal of geomagnetism and geoelectricity","volume":"11 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1997-06-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127727382","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: 14
Two-Dimensional Inversion of Papua New Guinea Magnetotelluric Dataset Assuming Static Shift as a Gaussian Distribution 假设静态偏移为高斯分布的巴布亚新几内亚大地电磁数据集二维反演
Journal of geomagnetism and geoelectricity Pub Date : 1997-06-20 DOI: 10.5636/JGG.49.857
Y. Ogawa
{"title":"Two-Dimensional Inversion of Papua New Guinea Magnetotelluric Dataset Assuming Static Shift as a Gaussian Distribution","authors":"Y. Ogawa","doi":"10.5636/JGG.49.857","DOIUrl":"https://doi.org/10.5636/JGG.49.857","url":null,"abstract":"The Papua New Guinea Magnetotelluric dataset was analyzed by applying Groom-Bailey tensor decomposition, and a consistent strike direction of N66° W was determined. The dataset was approximated by two-dimensional impedances, and frequency independent twist and shear. The static shift parameters (local anisotropy and site gain) were determined using a two-dimensional inversion where static shifts were also part of the model parameters. The model misfit was simultaneously minimized together with the following two norms: (1) roughness norm of the model, and (2) static shift L2 norm. The trade-off parameters between the model misfit and these norms were determined so as to minimize the Akaike's Bayesian Information Criterion (ABIC).","PeriodicalId":156587,"journal":{"name":"Journal of geomagnetism and geoelectricity","volume":"49 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1997-06-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133421905","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: 7
Electric and Magnetic Field Galvanic Distortion Decomposition of BC87 Data. BC87数据的电场和磁场畸变分解。
Journal of geomagnetism and geoelectricity Pub Date : 1997-06-20 DOI: 10.5636/JGG.49.767
A. Chave, A. Jones
{"title":"Electric and Magnetic Field Galvanic Distortion Decomposition of BC87 Data.","authors":"A. Chave, A. Jones","doi":"10.5636/JGG.49.767","DOIUrl":"https://doi.org/10.5636/JGG.49.767","url":null,"abstract":"The BC87 magnetotelluric data exhibit distortions due to three-dimensional structures at all scale sizes, from very local to regional. Previous work has shown that these distortions can sometimes, but not always, be described by an electric field galvanic distortion model, and hence can be removed using a tensor decomposition approach. This work extends the analysis to include galvanic distortion of the magnetic field, and shows its importance for many of the BC87 sites. However, even a combined electric and magnetic field galvanic distortion approach fails for quite a few of the sites studied. This is pervasive for periods shorter than 10 s, suggesting local 3D inductive effects, but model inadequacy at longer periods may indicate a breakdown of the model assumptions, particularly the requirement that the regional electric field be both uniform across the distorting body and comparable to that at the observation point.","PeriodicalId":156587,"journal":{"name":"Journal of geomagnetism and geoelectricity","volume":"55 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1997-06-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126000267","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: 44
Two-Dimensional Forward Modeling of the NACP Anomaly (COPROD2R Data). NACP异常的二维正演模拟(COPROD2R数据)。
Journal of geomagnetism and geoelectricity Pub Date : 1997-06-20 DOI: 10.5636/JGG.49.739
J. Pous, J. Ledo, Á. Marcuello, P. Queralt
{"title":"Two-Dimensional Forward Modeling of the NACP Anomaly (COPROD2R Data).","authors":"J. Pous, J. Ledo, Á. Marcuello, P. Queralt","doi":"10.5636/JGG.49.739","DOIUrl":"https://doi.org/10.5636/JGG.49.739","url":null,"abstract":"A two-dimensional resistivity model was obtained for the COPROD2R data set by trial-and-error forward model fitting of the apparent resistivities and phases. Two major conductivity zones were found to explain the data in the zone where the NACP anomaly is located. The first one coincides with previous interpretations of the NACP anomaly, which results in four separate conductive bodies. The second is another deeper conductor, whose top is located at 26 km depth with its base deeper than 40 km. A test removing this deeper conductor was made in order to ensure its detectability.","PeriodicalId":156587,"journal":{"name":"Journal of geomagnetism and geoelectricity","volume":"38 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1997-06-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116391968","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: 2
Two-Dimensional Inversion of Papua New Guinea Data Using 'Least-Blocked' Models 利用“最小阻塞”模式对巴布亚新几内亚数据进行二维反演
Journal of geomagnetism and geoelectricity Pub Date : 1997-06-20 DOI: 10.5636/JGG.49.827
A. K. Agarwal, J. T. Weaver
{"title":"Two-Dimensional Inversion of Papua New Guinea Data Using 'Least-Blocked' Models","authors":"A. K. Agarwal, J. T. Weaver","doi":"10.5636/JGG.49.827","DOIUrl":"https://doi.org/10.5636/JGG.49.827","url":null,"abstract":"Magnetotelluric data obtained from a region of Papua New Guinea have been inverted with the aid of a two-dimensional scheme in which the simplest 'least-blocked' model compatible with the data is sought. The average strike direction for the entire region and for all periods is estimated to be approximately N60W. In the rotated frame skew is small everywhere, but ellipticity values remain quite large at some sites, which raises some uncertainty about the assumption of two-dimensionality. Since the data also indicate the presence of local galvanic distortion, a static shift correction has been applied; both the original (rotated) data and the static-shift corrected data have been used to generate 'least-blocked' models. The final models for the two data sets are found to resemble each other quite closely. Both reveal a descending conductive layer beneath a resistive limestone cover of thickness 0.6-0.8 km on southwestern side of the profile increasing to around 2.1-2.4 km on the northeastern side. The one notable difference is that the descending conductive layer divides into two parts separated by a resistive limestone layer in the model obtained from static-shift corrected data, but not in the other.","PeriodicalId":156587,"journal":{"name":"Journal of geomagnetism and geoelectricity","volume":"4 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1997-06-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130994177","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: 5
Data-Adaptive Inversion of the Oklahoma EMAP Dataset. 俄克拉荷马州EMAP数据集的数据自适应反演。
Journal of geomagnetism and geoelectricity Pub Date : 1997-06-20 DOI: 10.5636/JGG.49.801
Y. Ogawa
{"title":"Data-Adaptive Inversion of the Oklahoma EMAP Dataset.","authors":"Y. Ogawa","doi":"10.5636/JGG.49.801","DOIUrl":"https://doi.org/10.5636/JGG.49.801","url":null,"abstract":"The Oklahoma EMAP dataset was analyzed using a two-dimensional inversion algorithm which includes static shifts as free parameters. Model misfit was minimized while simultaneously minimizing the resistivity roughness norm and the static shift L2 norm. The tradeoff parameters between the model misfit and these two norms were determined to minimize the Akaike's Bayesian Information Criterion (ABIC).","PeriodicalId":156587,"journal":{"name":"Journal of geomagnetism and geoelectricity","volume":"403 1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1997-06-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123257877","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: 2
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