地质力学磁力模型试验中均匀梯度磁场的构建

地质力学磁力模型试验利用电磁力（场）模拟重力（场）的原理研究地质力学工程问题,采用的相似材料由铁磁材料与岩土体混合而成。铁磁材料在磁场中的受力方向和大小与所处空间的磁通密度梯度的大小和方向有关,为了模拟均匀的重力场,需要得到在一定空间范围内磁通密度梯度大小相同、方向单一的磁场。根据电磁学基本原理,构建了3种磁路形式以获得磁通密度梯度相对均匀的磁场,对磁力模型试验相似材料进行加载。对比3种磁路,在最佳试验区内开放式磁路对磁场的利用率更高,所以在电流相同条件下等到的磁通密度梯度的量值也更大。与另两种磁路形式相比,尽管半开放式磁路在重量和工作效率上的性能不及开放式和封闭式磁路,但其最佳试验空间的磁通密度梯度的均匀性最好,误差在5%以内,半开放式磁路可以作为地质力学磁力模型试验的磁场发生装置。     

磁偶极子存在时导电水平圆柱体的场

将磁偶极子在导电水平圆柱体的场分解为单磁极的一次场、二次场、柱内场、柱外场。然后,由两个单磁极的场叠加而得到磁偶极子的场,并编程序对总场的频率响应函数的虚实分量二次磁场分别做了计算。     

确定地下管线深度的方法原理研究

从理论上阐述了利用倾斜磁场最大值点、利用垂直磁场分量峰值点和利用水平磁场分量半极值点确定地下管线深度的原理方法,指出了利用倾斜磁场最大值点确定管线深度时在原理上存在的问题和不实用性,同时从原理上和实用中筛选出了最佳的定深方法-水平磁场分量三角法.     

The influence of the inclination of the accretor’s magnetic axis on the accretion-disk structure in intermediate polars

Typical changes of the accretion-disk structures in intermediate polars are studied as a function of the inclination of the accretor’s magnetic field. Thre-dimensional numerical modeling was performed for seven differentmagnetic-axis inclinations. The results showthat the system forms a magnetosphere region, and that column accretion occurs. The action of the magnetic field tilts the inner parts of the disk along the magnetic axis of the accretor. The magnetic-field inclination appreciably influences matter transfer in the disk and accretion processes. Generation of toroidal magnetic field, magnetic braking, and alignment of the dipole magnetic field result in oscillations of the accretion rate. A direct relationship between the field inclination and the oscillation amplitude is found, as well as an inverse relationship between the field inclination and the oscillation period.     

浅水中磁性柱状体的磁场特征

在某些浅水区域中, 常有大量工程障碍, 如磁性柱状体。依据磁性柱状体的特点, 从顺轴磁化无限延深柱状磁性体这一简化数学模型的磁场分析入手, 进而对更近实际的顺轴磁化有限延深柱状磁性体的磁场及其梯度场的分布规律进行讨论, 并据此提出了采用水平磁梯度测量法对磁性柱状体磁特性实施探测的可取途径。     

磁法探测上海市掩埋煤气凝水井

本文论述了在城市中探测掩埋煤气凝水井的一种磁测方法,对由凝水井产生的磁场及磁场梯度进行了正演计算,对城市环境中的干扰背景磁场进行了理论分析,指出采用磁梯度探测方法能够有效的压制干扰背景磁场,突出有效异常,是城市中进行磁法探测的一种简便有效的方法。文中还就探测方法及磁梯度异常的反演计算进行了讨论。     

The Two-Layer Geodynamo Model

A 2-D mean field geodynamo model with the algebraic form of nonlinearity is considered. The geostrophic alpha-effect and differential rotation are taken from the 3-D models of convection in the liquid core of the Earth. The analysis reveals that these both are located in different spatial areas, and their correlation is no more than ten percent. The model allows typical Z-distributions of the poloidal magnetic field to be generated within the Taylor cylinder. On the surface, this field configuration corresponds to the magnetic dipole. Because of the spatial homogeneity of the magnetic field in the cylinder, dissipation of the field is small, which causes its greater amplitude in this region. Owing to the simple form of alpha-effect quenching by the magnetic field, the model can be used to generate a magnetic field over geological times.     

煤体静载破坏中低频磁场变化特征及产生机制研究

为了研究煤体静载破坏中低频磁场变化特征及其产生机制,进一步完善煤矿动力灾害监测预警技术,通过室内试验、现场试验研究了煤体静载破坏中低频磁场时、频谱特征,并结合微震信号提出了低频磁信号的产生机制。结果表明：煤体静载破坏中所产生低频磁场信号强度为19～156 nT,信号最大幅值、能量与试样强度、加载速度均呈正相关关系。垂直于裂纹扩展面磁场最强,平行于裂纹扩展面磁场最弱。并结果微震信号提出了低频磁场产生机制。低频磁场与微震信号具有时、频域同步性,带电裂纹面随微震信号同频振荡为低频磁场产生机制。现场放炮破煤低频磁信号由簇状脉冲信号及小幅震荡信号组成,其中簇状脉冲成分产生于炮后振动波带动带电壁面的同频振动,而小幅震荡成分是巷帮煤壁趋向新应力平衡状态时发生的横向拉伸破坏及带电煤碎屑运移、摩擦及转动的结果。     

A new approach to modeling the surface magnetic fields of chemically peculiar stars

A reconstruction of the line-of-sight component and modulus of the surface-magnetic-field vector is proposed, using a model with artificial point sources of the magnetic field with “virtual” magnetic charges in the body of a star. This approach for the direct calculation of the field from the superposition of the potentials of individual magnetic charges enables the reconstruction of most possible configurations of the surface magnetic field of a star. Proper choice of the axis orientations for the three coordinate systems used makes it possible to obtain a simple representation for the vector components of the surface magnetic field. In a dipole approximation, the expression for the line-of-sight component of the magnetic field averaged over the visible disk of the star reduces to the form obtained in other studies.     

Active longitudes and north-south asymmetry of the activity the Sun as manifestations of its relic magnetic field

The distributions of dominant magnetic polarities in synoptic maps of photospheric magnetic fields and their extrapolations to the corona based on Stanford Observatory data are studied. Both dipolar and quadrupolar magnetic patterns are detected in the distributions of dominant polarities in the near-equatorial region of the photosphere for activity cycles 21, 22, and 23. The field in these patterns often has opposite signs on opposite sides of the equator, with this sign changing from cycle to cycle. A longitude-time analysis of variations of the mean solar magnetic field shows that the contribution of the large-scale magnetic patterns to the total field does not exceed 20 µT. The most stable magnetic structures at a quasi-source surface in the solar corona are separated by approximately 180° in heliographic longitude and are close to dipolar. The nature and behavior of these large-scale magnetic patterns are interpreted as a superposition of cyclic dynamo modes and the nonaxially symmetric relic field of the Sun. The contribution of the relic field to the mean solar magnetic field appears as a weak but stable rotational modulation whose amplitude does not exceed 8 µT.     

Variations of the dipole magnetic moment of the sun during the solar activity cycle

Observations of the large-scale solar magnetic field (synoptic maps) and measurements of the magnetic field of the Sun as a star (the total magnetic field) are used to determine the dipole magnetic moment and direction of the dipole field for three successive solar cycles. Both the magnetic moment and its vertical and horizontal components vary regularly during the cycle, but never disappear completely. A wavelet analysis of the total magnetic field shows that the amplitude of the 27-day variations of this field is very closely related to the magnetic moment of the horizontal dipole. The reversal of the global dipole field corresponds to a change in the inclination of its axis and occurs in a series of steps lasting one to two years rather than continuously. Before the onset of the reversal, the dipole axis precesses relative to the solar rotational axis, then shifts in a meridianal plane, reaching very low latitudes, where a substantial shift in longitude then begins. These results are discussed in connection with helioseismological data indicating the existence of oscillations with a period of about 1.3 yr and properties of dynamo processes for the case of an inclined rotator.     

Impact of the magnetic field on the structure of accretion disks in semi-detached binaries

We discuss characteristic features of the magnetic gas-dynamical structure of the flows in a semi-detached binary system obtained from three-dimensional simulations, assuming that the intrinsic magnetic field of the accreting star is dipolar. The turbulent diffusion of the magnetic field is taken into account. The SS Cyg system is considered as an example. Including the magnetic field can alter the basic parameters of the accretion disk, such as the accretion rate and the characteristic density. The magnetic field in the disk is primarily toroidal.     

The increase in the magnetic flux from the polar regions of the Sun over the last 120 years

The latitudes of the zonal boundaries of the global magnetic field of the Sun are determined from the magnetic neutral lines on synoptic Hα maps obtained during 1878–1999. The area of the polar zone occupied by magnetic field of a single polarity at solar minima has doubled over the last 120 years. This provides an explanation for the secular increase in heliospheric characteristics, which differs from the two-fold increase of the magnetic field strength predicted for this period. The temporal variations of the magnetic flux from the polar regions and their role in global changes of the Earth’s climate are discussed in connection with secular variations in the structure of the internal magnetic field of the Sun.     

The hanle effect in a turbulent magnetic field

Exact analytical expressions for the scattering phase matrix are presented for various models of a turbulent magnetic field having a symmetry axis in the solar atmosphere. The polarization of the scattered radiation in the plane of the scattering is shown to be virtually independent of the predominant direction of the turbulent magnetic field. The Hanle effect does not operate in a longitudinal magnetic field normal to the surface of the atmosphere, since the phase matrix has the form of a resonance phase matrix with zero magnetic field.     

The theory of bypassed-isotope formation in the universe

A Fermi-gas model for the atomic nucleus in the presence of a quantizing magnetic field is considered. The energy of the magnetized neutrons is determined taking into account the Pauli paramagnetism, and the energy of the magnetized protons taking into account Landau diamagnetism and Pauli paramagnetism. To determine the characteristics of the proton-gas energy in a quantizing magnetic field, we use a model for the proton motion in which the initial energy of the proton and the magnetic field strength enable estimation of the maximum Landau quantum number. The latter characterizes the proton motion perpendicular to the direction of the magnetic field. Due to the occupation of Landau levels by protons, it is possible to estimate the kinetic energy for continuous motion along the magnetic field from zero to a certain finite value. As a result, the magnetic field of a certain strength facilitates neutron evaporation from the nucleus and increases the stability of the protons in the nucleus.     

1600-2000年地球主磁场的全球变化

根据汤普森（Thompson）地磁场模型和第 8代IGRF模型，计算了1600-2000年期间的偶极子磁场、非偶极子磁场、西向漂移和地磁功率谱等反映主磁场变化的主要参数，分析了各个参数的长期变化特征。主要结果是：400年来地磁场的偶极子磁矩持续减小，1800年以来磁心的位置快速离开地心向太平洋方向移动了291km；西向漂移有大约30年左右的周期；非偶极子磁场异常中，南大西洋正磁异常、非洲负磁异常和大洋洲负磁异常是1600年以来一直存在的 3个大型磁异常，东亚正磁异常和北美正磁异常是1700年后逐渐形成的，17世纪北太平洋地区存在强的正磁异常。     

关于磁法勘探测点坐标的生成与工作部署图绘制

在磁法勘探中,测点坐标的批量生成是必不可少的环节.提出了利用Visual C++编制程序生成1∶5万高精度磁法勘探测点坐标的思路,并编程加以实现;利用MapGIS的空间分析和投影变换功能实现了野外工作部署图的绘制.最后,将此方法应用于国家地调项目四川通安-小牛场地区远景调查项目磁测工作中.实践证明,此方法在工作中取得了较好的效果.     

航磁测量飞机飞行姿态影响及矫正

为消除航磁测量过程中由于飞机姿态变化而产生的感应磁场、涡流磁场等磁干扰,本文建立了干扰场模型,用补偿的方法对飞机飞行姿态产生的影响进行矫正。为验证方法的有效性,对M区实测航磁数据进行实时姿态矫正处理,结果显示,处理后的磁总场数据与国际标准地磁场基本吻合。证明本文提出的实时补偿方法能够消除飞机飞行姿态对磁测质量的影响。     

地面磁测数据正常场改正现行方法探讨

地面磁测数据正常场改正是地面磁测工作资料整理的一个不可或缺的步骤。正常场改正的好与坏、对与错,改正的程度如何,都直接关系到磁异常的形态,以至于磁测工作的解释结果。本文通过讨论国际地磁参考场的求法、地面磁测工作正常场的改正意义,比较了国际地磁参考场与地磁图的精度,对现行的地面磁测数据正常改正的方法探讨后,通过工作实例说明...     

磁法勘探的科技进展

本文从地面磁测、航空磁测、海域磁测、岩石磁性及古地磁研究、地磁绝对测量、磁异常数据处理和解释理论以及发展趋势等方面,综述了磁法勘探科技在我国的进展情况。