Magnetic interpretation of pairs of sheets and their equivalence to dykes     

S. K. G. Krishnamacharyulu  Bh. V. V. Gopalarao  I. V. Radhakrishna Murthy 《Pure and Applied Geophysics》1990,132(4):719-731

Magnetic anomaly profiles over two thin sheets separated by a small distance resemble those of dykes andvice versa. Interpretation of anomalies over a pair of sheets based on the magnetic properties of dykes predicts a dyke whose centre lies midway between the positions of the sheets. The dyke, on the other hand, is magnetically equivalent to a pair of sheets, both lying at the same depth and having the same magnetization.The magnetic anomalies due to a pair of sheets can be interpreted by framing linear equations between the anomalies and their distances measured from an arbitrary reference. Application of this method to anomalies of dipping sheets with a finite depth extent is indicated.  相似文献   

地球远磁尾中的磁场重联(Ⅰ)流动撕裂模不稳定性     

王水  郑惠南 《地球物理学报》1991,(6)

本文数值研究了地球远磁尾中流动撕裂模不稳定性所引起的磁场重联过程.结果表明,在短暂的指数增长之后,当磁岛宽度接近等离子体片厚度时,流动撕裂模不稳定性的增长率大大降低,最终磁岛宽度趋于饱和.磁岛的饱和宽度随着磁Reynolds数S的增大而减小,随着剪切流动层宽度δV的增大而增加.在S→∞的情况下,流动撕裂模将退化为流动颈缩模,磁场重联不再发生.当飞船通过由流动撕裂模不稳定性所形成的磁岛时,即可观测到磁场B_z分量由北转南或由南转北的现象.  相似文献   

Sq外源和内源电流体系的经度效应和UT变化   总被引：4，自引：0，他引：4       下载免费PDF全文

徐文耀  李卫东 《地球物理学报》1994,37(4):440-447

根据ＩＧＹ／ＩＧＣ期间全球地磁台网以及中国地磁台站的资料，计算出每－ＵＴ小时的Ｓ_ｑ外源和内源电流体系．对Ｓ_ｑ电流体系ＵＴ变化和经度效应的分析研究表明，Ｓ_ｑ外源电流体系的空间图案没有显著的ＵＴ变化，电流涡焦点的地理纬度与磁赤道有密切关系，其变化范围，北半球为２５°－３５°Ｎ，南半球为３０°－４２．５°Ｓ．外源电流总强度的平均值为２２９ｋＡ（北半球）和１７３ｋＡ（南半球），其变化范围为±５０ｋＡ（北半球）和±４０ｋＡ（南半球）．Ｓ_ｑ内源电流体系的图案和强度有显著的ＵＴ变化，电流体系焦点纬度有类似于外源电流系的变化．在大西洋、印度洋、北太平洋地区，内源电流体系的总强度明显小于大陆地区的内源电流强度，表明这些大洋地区上地幔电导率低于大陆地区．  相似文献   

驱动重联过程中等离子体团的聚合          下载免费PDF全文

金曙平  师立勤 《地球物理学报》1994,37(1):1-9

本文对驱动重联过程作了二维可压缩磁流体动力学模拟．对于长的计算域（１：４），在持续入流的作用下形成了双重磁岛结构，这些磁岛在向外运动的过程中不断靠近，逐渐聚合成为一个大的等离子体团，并继续向外运动．这说明在地球磁层顶和磁尾所观测到的大尺度磁结构，很可能是在驱动重联过程中，由较小的等离子体团聚合后形成的．并初步揭示了在空间等离子体中，磁岛的聚合过程难以直接观测的动力学原因．  相似文献   

任意阶次磁多极子场力线方程的解析表示          下载免费PDF全文

马石庄 《地球物理学报》1994,37(5):703-706

本文证明任意阶次磁多极子场力线方程总可以用有限形式解析地表示，并对偶极族和四极族磁多极子场力线的位形给予注记。  相似文献   

A two-stage evolution of Visakhapatnam-Paradip shelf,east coast of India,from magnetic studies     

A S Subrahmanyam  K S R Murphy  T C S Rao  M M Malleswara Rao  S Lakshminarayana  K Venkateswarlu 《Journal of Earth System Science》1994,103(1):17-26

A detailed analysis of bathymetry and magnetic data of Visakhapatnam-Paradip shelf, east coast of India revealed three major structural lineaments over the shelf/slope of the area. Models derived from the anomalies associated with the trends indicate that trend A represents horst and graben type continental basement while trend B is due to a series of dyke intrusions. Trend C off Chilka lake forms the northward extension of 85°E lineation from deep sea Bengal Fan. A two stage evolution of the eastern continental margin of India has been inferred from the study of this part of the margin, viz., the rift stage evidenced by dyke intrusions of reverse polarity located within the inner part of the shelf and post-rift stage characterized by vertical tectonics in the form of a horst and graben type continental basement. The hotspot related aseismic 85°E ridge further complicated the tectonics of this part of the area.  相似文献   

中国松辽盆地白垩纪岩石磁化率、剩磁强度与古气候意义   总被引：9，自引：0，他引：9       下载免费PDF全文

方大钧  叶德泉 《地球物理学报》1989,32(1):111-114

本文对中国松辽盆地白垩系沙河子组、营城组、登娄库组、泉头组、青山口组、姚家组、嫩江组岩石进行了古地磁系统采样,采样地区主要在松辽盆地中部、北部的大庆油田主要勘探开发区及吉林东部营城煤矿煤田钻井。采样钻井分布在西起齐齐哈尔、白城,东至哈尔滨一带的广大区域内,共计22个钻孔。对其中900余块岩样进行了磁化率、剩磁强度测量(表1),并统计了白垩系各个岩段的平均磁化率(表2)。  相似文献   

Structures caused by repeated freezing and thawing in various loamy sediments: A comparison of active,fossil and experimental data     

Brigitte Van Vliet-Lanoë  Jean-Pierre Coutard  Albert Pissart 《地球表面变化过程与地形》1984,9(6):553-565

In this paper, the authors present the results of both macroscopic and microscopic investigations on structure development created by repeated ice lensing in various loamy experiments. Experimental data are compared with observations performed on active forms in High Arctic and Alpine Mountain environments. Those observations are also compared with phenomena observed in fossil periglacial formations of Western Europe. Platy and short prismatic structure formation is bonded to the hydraulic and thermal conditions during ice segregation. When a long series of alternating freezing and thawing affects platy structures, the fabric evolves, also being influenced by slope and drainage conditions: cryoturbations, frostcreep, and gelifluction can appear. They are characterized by specific microfabrics which are better developed with an increasing number of cycles: this is clear in experiments where hydraulic and thermal parameters are better controlled. Vesicles are also a prominent characteristic of the surface horizon in experiments and arctic soils. The genesis of vesicles is discussed on the basis of new observations and is related to the mechanical collapse of frost-created aggregates under the mechanical work of soil air escape during soil saturation by water at thaw.  相似文献   

浅议中国黄土磁化率的物理意义   总被引：5，自引：0，他引：5  

孙继敏  丁仲礼 《地球物理学进展》1995,10(4):88-93

中国的陆相黄土地层连续地记录了第四纪以来的古气候变化。基于中国黄土磁化率曲线与深海氧同位素记录具有可比性这一事实，磁化率作为一种气候替代性指标在黄土研究中得到广泛的应用。但是，磁化率的物理意义仍不清楚。本文作者对陕西榆林蔡家沟剖面末次间冰期以来的风成沉积作了研究，指出黄土、古土壤的磁化率差异不仅与前人提出的碳酸盐淋失、空隙度变化、“就地”新生成磁性矿物等作用有关，而且还可能与有机质有重要关系。有机  相似文献   

激波在磁盔－电流片位场中的传播：（Ⅰ）激波与磁盔间的相互作用          下载免费PDF全文

刘航宇  魏奉思  张剑虹 《地球物理学报》1995,(4)

利用新近获得的子午面磁盔－电流片背景太阳风稳态解，对激波从盔底沿电流片方向往外传播时与磁盔间的相互作用进行了数值模拟研究，重要新结果是：１．磁盔的存在使受扰介质速度跃变中央出现下凹，随着激波传出磁盔区并沿电流片方向传播，速度下凹逐渐减弱以致消失；２．激波将磁盔拉长并把盔顶的环形（垂直赤道面）磁场带到行星际空间，成为行星际磁场南向分量的来源之一；３．５个太阳半径（Ｒ⊙）内的磁盔部分将出现精细结构，沿盔外边界形成两条高速带，以及马蹄形密度（亮）环形结构等．这些结果表明，太阳附近高速等离子体与磁盔间存在重要的动力学相互作用过程，对行星际空间的太阳风三维结构有重要影响．  相似文献