地球电场与地球磁场的形成机理

为探讨地球磁场的形成机理,应用经典电磁理论以微分的思维方式建立起三种自激发电机模型,用球形自激发电机模型简明地描述地球磁场的形成和分布;从分析地轴参考系中相对于自转地球静止的电荷间洛仑兹力的特点以及地球上的电荷在地球电场和地球磁场作用下的漂移规律,阐述中心磁场的形成及反转机理;分析电荷相对于地球的漂移以阐述偏磁场的形成.理论分析表明:地球上每一点的磁场都可以看成是由该点的几个分磁场叠加而成;地球具有自身的电场;地球电场与地球磁场同时产生、同时变化,且都源自于地球的自转和地球上正负电荷的非对等分布.     

The deviation of the total geomagnetic field direction from the dipole field direction as a manifestation of the non-dipole field

Summary The angle between the total geomagnetic field direction and the axial dipole field direction was computed for the whole of the Earth's surface for the epoch 1945. It was supposed that the dipole field exerts a latitude-dependent influence on the surface manifestation of the non-dipole field. A modifying function of latitude was estimated to eliminate this influence. The isolines of the resulting quantity were plotted.     

地磁正常场的选取与地磁异常场的计算

根据2003年中国地磁观测数据（包括135年地磁测点和35个地磁台）以及我国邻近地区38个IGRF计算点的地磁数据,计算中国地磁异常场的分布。选取两种地磁场模型作为地磁正常场,一是国际参考地磁场的球谐模型,二是中国地磁场泰勒多项式模型。根据各个测点的地磁异常值（观测值减去模型计算值）,用球冠谐分析方法计算地磁异常场的球冠谐模型,并绘制2003年中国地磁异常（△D,△I,△F,△X,△Y,△Z）。分析和讨论了中国地磁异常场。     

日面方位磁场扰动和行星际磁场螺旋结构

文采用球坐标下2.5维理想MHD模型,对日球子午面内方位磁场扰动的传播进行数值模拟,重点分析它对行星际磁场螺旋角的影响. 本文认为,观测到的行星际磁场螺旋角大于Parker模型的预言值,是太阳表面不断向行星际发出同向方位磁场扰动的结果;太阳较差自转在太阳内部产生的方位磁场为这类扰动提供了源头. 模拟结果表明,采用持续时间等于周期的十分之一、扰动幅度为103nT量级的正向方位磁场扰动,就可使1 AU处行星际磁场的螺旋角增加2°左右,与有关观测结果相符. 模拟结果还表明,上述方位磁场扰动对日球子午面内的太阳风特性和磁场位形的影响基本上可以忽略.     

Spatial power spectra of the crustal geomagnetic field and core geomagnetic field

Lowes (1966, 1974) has introduced the function R_n defined by $\text{R}{}^{\mathrm{n}}\text{=(n + 1)}\text{∑}\text{m=0}\text{∞}\text{[(g}{}^{\mathrm{m}}{}_{\mathrm{n}}\text{)}{}^2\text{+ (h}{}^{\mathrm{m}}{}_{\mathrm{n}}\text{)}{}^2\text{]}\text{where}\text{g}{}_{\mathrm{n}}{}^{\mathrm{m}}\text{and}\text{h}{}_{\mathrm{n}}{}^{\mathrm{m}}$ are the coefficients of a spherical harmonic expansion of the scalar potential of the geomagnetic field at the Earth's surface. The mean squared value of the magnetic field B = ??V on a sphere of radius r > α is given by $\text{〈}\text{B}\text{·〉 =}\text{∑}\text{n=1}\text{∞}\text{R}{}^{\mathrm{n}}\text{(}\text{a/}\text{r}\text{)}{}^{\mathrm{2n=4}}\text{where}\text{a}$ is the Earth's radius. We refer to R_n as the spherical harmonic spatial power spectrum of the geomagnetic field.In this paper it is shown that Rⁿ = R^M_n = R^C_n where the components R_n^M due to the main (or core) field and R_n^C due to the crustal field are given approximately by $\text{R}{}^{\mathrm{M}}{}_{\mathrm{n}}\text{= [}\text{(n =1)/}\text{(n + 2)}\text{](1.142 × 10}{}^9\text{)(0.288}{}^{\mathrm{n}}\text{Λ}{}^2\text{R}{}^{\mathrm{C}}{}_{\mathrm{n}}\text{= [}\text{(n =1){[1 — exp(-n/290)]/}\text{(n/290)} 0.52 Λ}{}^2\text{where}\text{Iγ = 1 nT}$. The two components are approximately equal for n = 15.Lowes has given equations for the core and crustal field spectra. His equation for the crustal field spectrum is significantly different from the one given here. The equation given in this paper is in better agreement with data obtained on the POGO spacecraft and with data for the crustal field given by Alldredge et al. (1963).The equations for the main and crustal geomagnetic field spectra are consistent with data for the core field given by Peddie and Fabiano (1976) and data for the crustal field given by Alldredge et al. The equations are based on a statistical model that makes use of the principle of equipartition of energy and predicts the shape of both the crustal and core spectra. The model also predicts the core radius accurately. The numerical values given by the equations are not strongly dependent on the model.Equations relating average great circle power spectra of the geomagnetic field components to R_n are derived. The three field components are in the radial direction, along the great circle track, and perpendicular to the first two. These equations can, in principle, be inverted to compute the R_n for celestial bodies from average great circle power spectra of the magnetic field components.     

Secular variations in the main geomagnetic field within the scope of the dynamic model of field sources

The effect of different-level sources on the spatial structure of the secular variations has been considered based on the dynamic model of sources of the main geomagnetic field developed by us. It has been obtained that the development of 13 most powerful dipoles only roughly characterizes global anomalies of the secular variations, and each anomaly results from the superposition of the dynamics of several sources. The model secular variations have been compared with the data from the observatories. It has been obtained that it is impossible to describe local anomalies of the observed secular variations ignoring sources of the third order of smallness as compared to the main dipole. It has been assumed that topographic vortices, originating around inhomogeneities of the core-mantle boundary, can be physical sources responsible for dipoles of the third order.     

同场地多方位多极距地电场相关特性

针对5个典型地震震中周边的50余个场地记录到的地电场数据展开分析,计算了各场地不同方位之间的地电场相关系数δ_xy或同方位不同极距之间的地电场相关系数δ_xx,以此表征场地地电场变化的复杂性。结果显示:地震活动平静期间这些场地的地电场相关系数δ_xy和δ_xx 具有相对稳定性,中强地震孕育发生期间震中附近多数场地的δ_xy和δ_xx会出现明显下降,且这种现象具有方向性、时间准同步性,并随着震中距的增加而逐步消失。从机理上推断,δ_xy和δ_xx的下降反映了震中附近局部场地地电场变化的非均匀性。      

渗流场参数与地震波场参数的关联关系研究综述

地球表层岩石是由不同尺度的岩石骨架、孔隙、以及孔隙中的流体物质相互作用形成的.研究含有孔隙和裂缝的复杂岩石介质中的地震波传播效应一直是石油地球物理勘探领域的热点.因此,许多学者对复杂岩石介质的渗流特征,和地震波的传播与衰减进行了大量的研究.本文在回顾孔隙介质的地震波的传播与衰减理论发展的基础上,首先介绍了孔弹介质的非局部Biot理论,并用它预测负频散现象,然后介绍了实验观测到的波的衰减与岩石物理性质(如孔隙度和渗透率)的关系,最后,给出了对渗流场和地震波的传播与衰减的认识,并对它们之间的相互关系做了一些展望.     

Dynamics of the magnetic field and velocity field in an emerging active region

The dynamics of the magnetic field and velocity field during the birth and an early development stage of a major active region is studied. SOHO MDI longitudinal-component magnetograms, Dopplergrams, and continuum images are used. The presence of an enhanced material upflow in the photosphere during the passing of the top of the magnetic flux loop, forming the active region, is revealed. The maximum upflow velosity is 2 km/s and the maximum size of the upflow area exceeds 20000 km. The lifetime of the upflow is about two hours. The undulating form of the magnetic flux tubes crossing the photosphere is confirmed. A structural-analysis technique is used to show that the trailing polarity field at the formation stage of the active region is more highly structured than the leading polarity field.     

An analysis of the palaeomagnetic field

Summary The paper is devoted to a critical evaluation of the hypothesis of the prevalent character of the palaeomagnetic field in the course of the whole Phanerozoic. The study ties in with the synthetic processing of all so far published palaeomagnetic data for Eurasia and Africa respecting some of the models ensuing from the concept of plate tectonics. Initial material for testing the dipolar hypothesis was obtained by statistical processing of the palaeomagnetic pole positions and by analyzing the values of the so-called palaeorotation, the palaeoinclination difference and of palaeodivergence. It was shown that, by defining tectonically stable blocks (plates, palaeoplates) within the scope of the Eurasian continent and within the scope of the African continent as a whole, data were obtained bringing evidence of the predominating dipolar character of the mean geomagnetic field for the period from the Quaternary to the Cambrian, with the exception of the Silurian which has not been studied sufficiently. The deviations of the palaeomagnetic directions from the direction of the dipolar field within the scope of the stable blocks have the character of a Gaussian distribution and the standard deviations only amount to a few degrees.     

火星感应磁场模型及其磁力线分布

本文利用火星具有电离层而无内禀磁场的特点以及它与太阳风相互作用的性质,通过适当的假设,建立了火星感应磁场模型.此模型建立如下,利用电流连续的特性: Δ·j=0 (j为感应电流)以及对火星磁层中的电流体系分布的合理假设给出电流,并由毕奥-萨伐尔定理得到火星周围的磁场强度的表达式;利用我们自编的磁力线跟踪程序由求得的磁场强度得到火星周围的磁力线分布.我们发现:利用此火星磁场模型得到的火星周围的磁力线分布与卫星观测的结果以及其他方法得到的结果符合的很好.     

Estimation of the normal geomagnetic field and geological interpretation of the normal field anomalies over middle-northern Croatia

Based on the ground survey of total-field magnetic data at 53 sites, which recorded a time-series over the interval 2003–2005, the core field + long wavelength lithospheric field over the middle-northern Croatia region was calculated. The area of the survey was 18900 km², an average distance between the neighbouring sites being 12 km. The results were reduced to 2004.5 epoch. This “normal” total-field was estimated using the firstorder Taylor polynomial as a function of geographic coordinates, and the polynomial coefficients were calculated with three methods of adjustment: simple and weighted least squares fits and adjustment according to the most frequent value. The stability of the normal field was tested using the Monte Carlo-type test, by decreasing the input data set in each adjustment (up to 90%). All obtained field residuals (measured-“normal”) were mutually compared, as well as fit coefficients of the Taylor polynomials. The residual values indicate the presence of shorter-wavelength anomalies, specifically three major residual anomalies were found (−106 nT, 74 nT and 57 nT). The geostatistical analysis of the ground survey data and the normal field residuals (respectively), using the median absolute deviation method, was further conducted in order to evaluate the calculated anomalies. The geological situation around the anomalies derived by the median absolute deviation method, and around the normal field residual anomalies, is given. The correlation was found between higher value anomalies of the normal field residuals, and shallow volcanic rocks and oil field, respectively.     

Eddington: leading the field

Sixty years after the death of Sir Arthur Eddington OM, FRS, the RAS held a Commemoration Meeting to recall his outstanding contributions to astronomy, cosmology and the popularization of science, organized by John D Barrow and Leon Mestel .     

小行星引力场综述

近年来小行星探测已成为各航天大国的热点,小行星引力场对研究其内部结构、组成成分、早期演化和探测器轨道设计、着陆等方面有着极其重要的作用.随着小行星探测数据的不断更新、探测任务的增多和观测技术改进,针对小行星引力场的研究也在不断增多并产生新的进展.目前获取小行星引力场的方法主要为利用探测器飞掠过程中得到的轨道跟踪数据反演...     

海洋地磁三分量测量技术

与拖曳式总场测量相比,海洋地磁三分量测量能够获得更多的地磁场矢量信息,并能通过船载测量在更大海区范围内进行.本文从船载三分量测量和拖曳三分量测量两个方面总结了国外的发展现状,分析了海洋地磁三分量测量中船磁(载体磁场)标定和载体定姿两个关键技术,并结合我国海洋磁测发展现状建议首先发展船载海洋地磁三分量测量系统.     

地球磁层的磁场模型

1958年卫星探测发现了磁层,至今已有半个世纪,对磁层电场、电流体系、磁场、粒子分布和等离子体波的探测研究构成了空间物理的重要内容,其结果是各种磁层模型的出现.本文简要综述磁层磁场建模的基本原理、方法和发展历史,对十几种重要的磁层模型的特点、局限性和适用范围进行了对比分析,以Tyganenko模型为例,讨论了磁层模型发展的趋势.     

Spherical harmonic analyses of the palaeomagnetic field

Analytical models of the palaeomagnetic field have been constructed for a number of geological periods (Quaternary Neogene, Jurassic, Triassic, Permian and Permo-Carboniferous) by spherical harmonic analysis using the present-day world map as a basis and (for the earlier periods) using also a palaeogeographic reconstruction. The use of the palaeogeographic chart for the earlier periods simplifies the models, and its use appears to be valid. The low accuracy, small number and uneven distribution of palaeomagnetic data severely limit the conclusions which can be drawn from the analyses. Nevertheless the results for all periods indicate that throughout the past 300 million years the geomagnetic field has maintained its global structure, and has remained similar to the field of a dipole slightly shifted from the Earth's centre. It appears that there have not been any persistent systematic anomalies or variations in the Earth's magnetic field throughout that time, but rather that the field has been oscillating around a mean level not greatly different from that of the present epoch.     

The macroseismic field of the Balkan area

A catalogue of 356 macroseimic maps which are available for the Balkan area was compiled, including information on the source parameters of the corresponding earthquakes, the macroseismic parameters of their strength and their macroseismic field. The data analysis of this catalogue yields new empirical relations for attenuation, which can be applied for the calibration of historical events, modelling of isoseismals and seismic hazard assessment. An appropriate analysis allowed the separation and estimation of the average values of the geometrical spreading, n, and anelastic attenuation factor, c, for the examined area which were found equal to –3.227 ± 0.112 and –0.0033 ± 0.0010. Scaling relations for the focal macroseismic intensity, I_f, and the epicentral intensity I₀, versus the earthquake moment magnitude were also determined for each Balkan country. A gradual decrease of the order of 0.5 to 1 intensity unit is demonstrated for recent (after 1970) earthquakes in Greece. Finally the depths of the examined earthquakes as they robustly determined (error <5 km) on the basis of macroseismic data were found to have small values ( 10 km). However large magnitude earthquakes show higher focal depths ( 25 km), in accordance with an increase of the seismic fault dimensions for such events.     

地球基本磁场的成因

在略高于古藤堡面的压力和温度条件下,地核物质中的原子结构状态发生了质变.如对于外层能级分布是3d64s2的铁原子而言,Fe原子的最外层和极少一部分Fe原子的次外层将受到破坏,使外层电子发生"公有化"现象,残破的原子(处于离子状态)在自引力作用形成的压力作用下,按原子密度的大小产生分异,"内核"多为显示有正电性能的密度较高的残破原子组成,"外核"(包含过渡层)为富含"公有化"电子而显示负电性能的密度相对较低的残破原子组成,这是一个地核物质量子状态变化的静态过程,从地球内部宏观电性结构看来,地球的"内核"和"外核"组成缮了一个静态的巨型似"原子球","外核"显示负电性,"内核"显示正电性,"内核"所带电量与"外核"所带电量相等,但符号相反,在静态的情况下,似"原子球"并不显示磁性.由于地球自转,"外核"上界面赤道上的自转线速度为252.9m/s,"内核"外界面赤道上的自转线速度为88.9 m/s,二者的速度差为164.0 m/s,这种含有由巨大电量的"外核"电子壳层相对"内核"绕固定的轴向(自转轴)转动,自然会形成它的基本磁场.