“Nonlinear energy stability in a compressible atmosphere”     

M. S. Chance  J. M. Greene  T. H. Jensen 《地球物理与天体物理流体动力学》2013,107(1-4):203-204

Abstract

A magnetic field line topology with nulls, generated by superimposing a uniform magnetic field onto the field from a distributed ring current, is analyzed. This simple model, which is reminiscent of the structures found in laboratory field reversed configurations and detached plasmoids, is amenable to substantial analytical progress and also facilitates the visualization of the three dimensional field geometry. Four nulls are seen to exist and representative field lines and tubes of flux found by numerical integration are presented. An infinite number of topologically distinct flux bundles is found. These are distinguished by the number of times they encircle a circular magnetic field line. A convenient mapping is described which proves very useful in distinguishing between and following the paths of the different tubes of flux as they traverse through the null system. The separatrices that divide these flux bundles are described. The complexities already present in this simple but nontrivial configuration serve to emphasize the difficulties in analyzing more complicated geometries, but the intuition gained from this study proves beneficial in those cases. One such example is the comparison of the generic features of our model with those found in a topologically different model of plasmoid formations in the earth's magnetotail.  相似文献   

西安地下热水开采现状与合理开发利用探讨   总被引：8，自引：0，他引：8  

金海峰  张益谦 《地球科学与环境学报》2004,26(3):40-43

西安市的热水井井深较大，投资费用高．延长地热井的使用寿命，对经济合理的开发地下热水则十分重要。根据对西安市多年地下热水动态的监测资料分析．西安市的地热井水头下降速度过大，尤以第三和第四热储层段更大，年均下降10余米，个别甚至达到37m。依据地下热水的埋藏特征和各井的分布及开采量情况分析，造成上述现象的主要原因是由于井距较近、开采层段集中和单井开采量过大所致。为使西安市的地下热水能可持续开发利用，提出合理布井、限量开采及地下热水的回灌等措施。  相似文献   

Distribution of stars perpendicular to the plane of the galaxy     

S. Chatterjee 《Journal of Astrophysics and Astronomy》1991,12(4):269-280

We present here rigorous analytical solutions for the Boltzmann-Poisson equation concerning the distribution of stars above the galactic plane. The number density of stars is considered to follow a behaviour n(m,0) ∼H(m - m₀)m^−x, wherem is the mass of a star andx an arbitrary exponent greater than 2 and also the velocity dispersion of the stars is assumed to behave as < v²(m)> ∼ m^−θ the exponent θ being arbitrary and positive. It is shown that an analytic expression can be found for the gravitational field K_z, in terms of confluent hypergeometric functions, the limiting trends being K_z∼z for z →0, while K_z → constant for z → infinity. We also study the behaviour of < |z(m)|²>,i.e. the dispersion of the distance from the galactic disc for the stars of massm. It is seen that the quantity < |z(m)|²>∼ m^t-θ, for m→ t, while it departs significantly from this harmonic oscillator behaviour for stars of lighter masses. It is suggested that observation of < |z(m)|²> can be used as a probe to findx and hence obtain information about the mass spectrum.  相似文献   

W3(OH)致密HⅡ区磁场研究     

周震浦 《中国天文和天体物理学报》1991,(2)

本文以W3(OH)为实例,建立了与OH脉泽成协的HII区气体-尘埃壳层的磁场模型,由此可见,致密HII区所在分子云核心中的磁场强度,与分子云核心的分子数密度之间存在指数α=1/2的幂律关系;而在HII区气体-尘埃壳层中,磁场强度与分子数密度之间存在α=1的正比关系,根据讨论可知,与OH脉泽成协的HII区,其气体-尘埃壳层的分子数密度为10~6cm~(-3)量级,磁场强度为几个mG;一旦分子数密度达10~7cm~(-3)量级,OH脉泽便将熄灭。  相似文献   

ICE, the electric field experiment on DEMETER   总被引：9，自引：0，他引：9  

J.J. Berthelier  M. Godefroy  M. Malingre  D. Lagoutte  F. Colin  C. Legendre  D. Benoist  J. Artru 《Planetary and Space Science》2006,54(5):456-471

  相似文献   

IAG2001年科学大会与大地测量学的最新进展     

胡建国  杨元喜  李建成  李金岭 《大地测量与地球动力学》2002,22(4):112-119

扼要报导了国际大地测量学术界的一次重要会议－IAG2001年科学大会。根据会议的学术报告，对坐标系统的统一与协调，全球重力场研究，导航卫星的应用，地壳形变与地球动力学等方面的研究进展作了详细介绍。  相似文献   

回转椭球电场问题一种新解法     

董豹  叶明建 《成都信息工程学院学报》1996,(Z1)

讨论关于回转椭球静态场求解的一般方法，借助回转椭圆坐标系，静态场问题的一般解可以用实宗量和虚宗量勒让德函数以及余弦函数形式表出，使得结果更为简明和系统化。所得结果可以直接应用到椭球导体电场、尖端效应、介质椭球极化以至双极化雷达测量降水问题等，具有相当具体的实用价值。  相似文献   

Three‐dimensional finite element analysis of the interaction between tunneling and pile foundations     

H. Mroueh  I. Shahrour 《国际地质力学数值与分析法杂志》2002,26(3):217-230

This paper concerns analysis of the impact of construction of urban tunnels on adjacent pile foundations. It is carried out using an elastoplastic three‐dimensional finite element modelling. Numerical simulations are performed in two stages, which concern, respectively, the application of the pile axial loading and the construction of the tunnel in presence of the pile foundations. Analysis is carried out for both single piles and groups of piles. Results of numerical simulations show that tunneling induces significant internal forces in adjacent piles. The distribution of internal forces depends mainly on the position of the pile tip regarding the tunnel horizontal axis and the distance of the pile axis from the centre of the tunnel. Analysis of the interaction between tunneling and a group of piles reveals a positive group effect with a high reduction of the internal forces in rear piles. Copyright © 2002 John Wiley & Sons, Ltd.  相似文献   

强磁场对中子星壳层热核反应的影响     

罗志全  彭秋和 《中国天文和天体物理学报》1996,(4)

本文通过考虑强磁场中电子的量子效应，分析了强磁场下电子气体的Fermi能，讨论了磁场对核的屏蔽势和核反应率的影响，进而计算了强磁场对天体物理中几个较重要的热核反应的影响，结果表明，相对于无磁场而言，在较低密度下，足够强的磁场使原子核的屏蔽势显著增加，但在ρ／μe＞10~5molcm~(-3)的密度下，中子星表面存在的强度为10~5～10~9T范围内的磁场对核反应率几乎没有影响。  相似文献   

长江三峡及邻区板内中强地震的孕震动力学分析     

张秋文 《大地测量与地球动力学》1994,(4)

本文在研究长江三峡及邻区地壳─上地幔结构和现今地壳重力场基础上，分析了该区板内中强地震的孕震动力学过程，探讨了整体上相对稳定的长江三峡及邻区孕育和发生中强地震的动力学机制，并提出了该区板内中强地震预测的动力学标志。  相似文献