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在地理坐标系下推导出二维电离层发电机理论方程,采用逐线迭代法求解得到全球二维电离层发电机电流函数,进而得到电离层发电机电流和电场.模式中使用的电导率是根据外部经验模式给出的背景大气和电离层参数,采用理论公式计算得出;输入的中性风场和磁场分别由HWM93和IGRF2000模型给出,该电离层发电机理论模式很好地给出了全球Sq电流形态及电离层E层发电机电场的基本特征.利用该模式研究了外部模式风场以及地磁场随高度的变化对模拟结果的影响,发现在90~180 km高度上,风场随高度变化对电流影响较大,而地磁场影响较小;重点模拟研究了地磁平静时期,Sq电流涡旋中心位置和总电流强度的变化规律,初步研究发现,电流中心位置在地理纬度±30°附近,不同的地方时电流随地磁纬度线平行移动,且南北半球两个电流涡中心电流强度之和变化不大.分析发现这种规律与发电机高度上的磁场总强度及地磁倾角的全球分布有很好的相关性. 相似文献
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Most of the current computing methods used to determine the magnetic field of a uniformly magnetized cuboid assume that the observation point is located in the upper half space without a source. However, such methods may generate analytical singularities for conditions of undulating terrain. Based on basic geomagnetic field theories, in this study an improved magnetic field expression is derived using an integration method of variable substitution, and all singularity problems for the entire space without a source are discussed and solved. This integration process is simpler than that of previous methods, and final integral results with a more uniform form. ΔT at all points in the source-free space can be calculated without requiring coordinate transformation; thus forward modeling is also simplified. Corresponding model tests indicate that the new magnetic field expression is more correct because there is no analytical singularity and can be used with undulating terrain. 相似文献
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通过地电场台址近地表介质电阻率和地电场值计算大地电流,从大地电流场中分离出涡旋电流;根据平面波理论和水平导电层模型,使用地磁暴观测数据在频率域计算地磁感应电场(GIE),由GIE计算地磁暴感应电流(GIC).计算结果与实测值对比分析表明:GIE计算结果与实测地电暴具有很好的相位一致性;GIC涡旋中心相对地电暴涡旋中心存在向SE漂移约3°的现象;磁暴时地磁场Z分量的幅值分布图中极大值区域与涡旋中心重合,可能是GIC涡旋中心偏移的原因.另外,根据电磁感应原理提出的等效环电流模型,在一定程度上解释了涡旋大地电流的形成机制.本项工作可应用于地磁观测与地电观测的相互校正,同时有助于认识地电暴对大地电流分布的影响. 相似文献
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利用地磁场全球模型MF6, EMM2010和基于地面观测数据建立的2010.0中国地磁参考场(CGRF2010)等3个模型分别计算了中国大陆地区岩石圈磁场, 发现3个模型各有其特点: 基于卫星数据建立的MF6模型分辨率有限, 其磁异常条带呈蠕虫状; EMM2010模型岩石圈磁场概貌与MF6模型相似但细节特征十分突出; CGRF2010模型可信度较高, 其分辨率东西部差异较大, 异常形态以团状为主． 通过分析3个模型得到的中国大陆地区岩石圈磁场垂直分量ΔZ的强度及其分布特征发现: ΔZ分量在准噶尔盆地、 塔里木盆地、 柴达木盆地及四川盆地等地区均为正值, 而在天山、 大巴山等地区为负值; ΔZ分量分布在华北岩石圈地块与华南岩石圈地块吻合程度较高; 在青藏高原南部、 西域岩石圈地块北部以及松辽岩石圈地块, 全球模型与CGRF2010模型存在显著差别． 相似文献
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本文选取了INTERMAGNET地磁台网2001年到2012年的地磁数据,对其进行世界时(UT)到地方时(LT)的转换后利用自然正交分量法(NOC)从所选资料中提取出太阳静日变化Sq成分,再通过球谐分析方法建立模型分离内、外源Sq成分,逐日反演出内、外源Sq等效电流体系,并得到外源Sq等效电流体系南北电流涡中心电流强度.本文将外源Sq等效电流体系南北电流涡中心电流强度与同一时期的Dst指数进行了对比分析,研究表明它们之间具有同步变化的规律,且北半球电流涡中心电流强度在磁暴发生时的异常现象远高于南半球.对F10.7cm太阳射电流量与外源Sq等效电流体系南、北半球电流涡中心电流强度的长短周期分析发现,Sq等效电流表现出明显的11年周期特点,与太阳活动周期一致.外源南、北半球电流涡中心电流强度和F10.7cm年均值的相关系数分别达到了0.93和0.90,说明太阳活动是导致外源Sq电流体系变化的最直接也最主要的因素,这可能与电离层电导率受控于太阳的电磁辐射相关. 相似文献
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为探索地磁长期变化中地磁急变事件的识别方法,分析地磁急变的特征,本文基于多个地磁台站子夜均值数据,利用线性拟合方法计算了地磁场X,Y和Z三个分量的年变率,对近年来发生的地磁急变事件进行了识别和分析。结果显示:Y分量能对分析时段内已报道的地磁急变事件进行很好的识别,其中1999年的地磁急变事件,在我国区域内发生的时间可能为1998年,此外2017年可能存在一个新的地磁急变事件;Z分量年变率整体变化平缓,2001年和2013年前后发生两次显著的地磁年变率变化,并且分别早于2003年和2014年两次显著的地磁急变事件时间,这与下地幔的高电导率层对不同分量地磁信号从核幔边界传播至地表过程中的延迟作用有关;X分量年变率出现多次地磁急变事件特征,其变化与Dst指数年变率变化具有相关性,可利用其去除X分量年变率中存在的外部空间电流体系影响成分,更可靠地辅助Y分量对地磁急变事件进行识别。总体上,地磁子夜均值数据年变率的空间分布与基于第12代国际地磁参考场（IGRF12）模型计算的地磁数据年变率的空间分布所呈现的变化特征在总趋势上具有一致性,表明地磁台站子夜均值数据能够反映我国区域地球主磁场的变化特征,而分别由子夜均值数据和IGRF12模型计算的2003年Y分量年变率空间分布均存在的显著局部特征,可能与地磁急变事件的区域特征有关。 相似文献
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V. V. Kalegaev K. Yu. Bakhmina I. I. Alexeev E. S. Belenkaya Ya. I. Feldstein N. V. Ganushkina 《Geomagnetism and Aeronomy》2008,48(6):747-758
The ring current dynamics during the magnetic storm has been studied in the work. The response of the magnetospheric current systems to the external influence of the solar wind, specifically, resulting in the development of the asymmetric ring current component, has been calculated using the magnetic field paraboloid model. The asymmetric ring current has been considered as a family of spatial current circuits in the Northern and Southern hemispheres, composed of the zones of the partial ring current in the geomagnetic equator plane, which close through the system of field-aligned currents into the ionosphere. The value of the total partial ring current has been estimated by comparing the calculated asymmetry of the magnetospheric magnetic field at the geomagnetic equator with the value of the Asym-H geomagnetic index. The variations in the symmetric and asymmetric components of the ring current magnetic field have been calculated for the magnetic storm of November 6–14, 2004. The contributions of the magnetospheric current systems to the Dst and AU geomagnetic indices have been calculated. 相似文献
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Cosmic ray (CR) fluxes, which penetrate into the Earth??s magnetosphere and atmosphere from the interplanetary space, are an important factor of space weather. The geomagnetic field allows or forbids CR particles to enter into a given point in the magnetosphere depending on their energy. The geomagnetic cutoff rigidity regulates the distribution of CR fluxes in the magnetosphere. The geomagnetic cutoff rigidity (geomagnetic threshold) determination accuracy is closely related to the accuracy of the magnetospheric model used in calculations. Using a method for tracing of charged CR particle trajectories in the magnetic field of a model magnetosphere, we obtained geomagnetic thresholds for two magnetosphere empirical models (Ts01 and Ts04), constructed based on the same initial database. The Ts01 model describes the middle magnetosphere for certain conditions in the solar wind and interplanetary field. The Ts04 model pays the main attention to describing the large-scale evolution of magnetospheric currents during a storm. The theoretically obtained geomagnetic thresholds have been compared with experimental thresholds, calculated using the spectrographic global survey method based on data from the global network of CR stations. The study has been performed for the period of a strong geomagnetic storm that occurred in November 2003. 相似文献
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对1900～2002年全球记录到的震级M≥4．0地震震中,利用IGRF（国际地球参考场）国际参考模型确定地磁场的特征。研究了主要地震活动带的地理学和内源引发的基本地磁场几何学之间的关系,查明了不同构造类型的地震活动带全球分布与地磁偏角或地磁场东-西向分量分布之间的构造对应。 相似文献
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中国地震局地球物理研究所与蒙古科学院天文与地球物理研究中心于2011—2012年合作开展了蒙古119个野外地磁测点的测量工作. 本文利用蒙古119个测点准确可靠的地磁数据, 分别加上9组边界点EMM2010模型计算值, 得到了蒙古2010.0年代地磁异常场的9个球冠谐和模型; 给出了地磁异常场北向分量ΔX、 东向分量ΔY和垂向分量ΔZ的等值线分布图, 并比较分析了这9个模型的异同; 同时计算了119个测点的地磁测量值与模型计算值之差的均方根误差σ, 以σ为指标来表征这9个模型的精度, 由此定量评价了边界点选取对模型精度的影响. 结果表明, 适当引入边界点能够提高模型精度, 而远离测区3°—5°的均匀边界点也能起到改善模型精度的作用. 因此在实际建模时, 应当在计算区域边界引入适当的边界点, 以改善地磁模型的精度. 相似文献
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High-performance computational models are required to make the real-time or faster than real-time numerical prediction of adverse space weather events and their influence on the geospace environment. The main objective in this article is to explore the application of programmable graphic processing units (GPUs) to the numerical space weather modeling for the study of solar wind background that is a crucial part in the numerical space weather modeling. GPU programming is realized for our Solar-Interplanetary-CESE MHD model (SIP-CESE MHD model) by numerically studying the solar corona/interplanetary solar wind. The global solar wind structures are obtained by the established GPU model with the magnetic field synoptic data as input. Meanwhile, the time-dependent solar surface boundary conditions derived from the method of characteristics and the mass flux limit are incorporated to couple the observation and the three-dimensional (3D) MHD model. The simulated evolution of the global structures for two Carrington rotations 2058 and 2062 is compared with solar observations and solar wind measurements from spacecraft near the Earth. The MHD model is also validated by comparison with the standard potential field source surface (PFSS) model. Comparisons show that the MHD results are in good overall agreement with coronal and interplanetary structures, including the size and distribution of coronal holes, the position and shape of the streamer belts, and the transition of the solar wind speeds and magnetic field polarities. 相似文献
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John V. Shebalin 《地球物理与天体物理流体动力学》2013,107(3):353-375
We consider an unforced, incompressible, turbulent magnetofluid constrained by concentric inner and outer spherical surfaces. We define a model system in which normal components of the velocity, magnetic field, vorticity, and electric current are zero on the boundaries. This choice allows us to find a set of Galerkin expansion functions that are common to both velocity and magnetic field, as well as vorticity and current. The model dynamical system represents magnetohydrodynamic (MHD) turbulence in a spherical domain and is analyzed by the methods similar to those applied to homogeneous MHD turbulence. We find a statistical theory of ideal (i.e. no dissipation) MHD turbulence analogous to that found in the homogeneous case, including the prediction of coherent structure in the form of a large-scale quasistationary magnetic field. This MHD dynamo depends on broken ergodicity, an effect that is enhanced when total magnetic helicity is increased relative to total energy. When dissipation is added and large scales are only weakly damped, quasiequilibrium may occur for long periods of time, so that the ideal theory is still pertinent on a global scale. Over longer periods of time, the selective decay of energy over magnetic helicity further enhances the effects of broken ergodicity. Thus, broken ergodicity is an essential mechanism and relative magnetic helicity is a critical parameter in this model MHD dynamo theory. 相似文献
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A possible mechanism of earthquake triggering by ionizing radiation of solar flares is considered. A theoretical model and results of numerical calculations of disturbance of electric field, electric current, and heat release in lithosphere associated with variation of ionosphere conductivity caused by absorption of ionizing radiation of solar flares are presented. A generation of geomagnetic field disturbances in a range of seconds/tens of seconds is possible as a result of large-scale perturbation of a conductivity of the bottom part of ionosphere in horizontal direction in the presence of external electric field. Amplitude-time characteristics of the geomagnetic disturbance depend upon a perturbation of integral conductivity of ionosphere. Depending on relation between integral Hall and Pedersen conductivities of disturbed ionosphere the oscillating and aperiodic modes of magnetic disturbances may be observed. For strong perturbations of the ionosphere conductivities amplitude of pulsations may obtain ~102 nT. In this case the amplitude of horizontal component of electric field on the Earth surface obtains 0.01 mV/m, electric current density in lithosphere –10–6 A/m2, and the power density of heat release produced by the generated current is 10–7 W/m3. It is shown that the absorption of ionizing radiation of solar flares can result in variations of a density of telluric currents in seismogenic faults comparable with a current density generated in the Earth crust by artificial pulsed power systems (geophysical MHD generator " Pamir-2” and electric pulsed facility " ERGU-600”), which provide regional earthquake triggering and spatiotemporal variation of seismic activity. Therefore, triggering of seismic events is possible not only by man-made pulsed power sources but also by the solar flares. The obtained results may be a physical basis for a novel approach to solve the problem of short-term earthquake prediction based on electromagnetic triggering phenomena. 相似文献
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T.S. Huang E. Romashets G. Le Y. Wang J.A. Slavin 《Journal of Atmospheric and Solar》2010,72(4):369-373
By using Tsyganenko's model for the magnetosphere's magnetic field, which links two hemispheres of the ionosphere, and adopting a practical boundary condition for the electric potential around the polar cap, we developed a new ionosphere–magnetosphere coupling model based on prairie view dynamo code (PVDC). The new model takes the variations in solar wind and interplanetary magnetic field, as well as the geomagnetic activity, into account. Rather than the previous version of PVDC that is useful only for quiet conditions, the new model enables to calculate the electric potential and currents in the ionosphere and the field-aligned current (FAC) off the ionosphere in quiet and disturbed times. Comparison of the calculated FAC with the measurements of Space Technology 5 (ST5) mission shows a good agreement. 相似文献
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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。 相似文献
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中国地区地磁场的球冠谐和分析 总被引：12，自引：11，他引：12
本文根据中国及其邻近地区的地磁三分量绝对测量资料,利用球冠谐和分析方法,计算出中国地区地磁剩余场的冠谐模型,地磁剩余场△X,△Y,△Z的模型均方根偏差分别为106.9,89.7,137.6 nT.提出由地磁场的国际参考地磁场和地磁剩余场的冠谐模型组成的联合模型作为中国参考地磁场的模型,它能较好地表示中国地磁场的分布.以地磁场的联合模型为正常背景场,计算出三分量磁异常的冠谐模型,并分析了磁异常的基本特征,它将为深入研究中国岩石层结构提供新证据. 相似文献
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本文利用CHAOS-6地磁场模型计算1997—2016年中国大陆地区34个地磁台站模型值,分析比较模型计算值与台站实测值之间的差异,利用国际参考场模型IGRF12计算结果进行佐证。结果表明:地磁异常场模量△T作为地磁台站观测环境的一种标志,年变化显示:①中国大陆地区34个地磁基准台绝大部分位于地磁正常区或弱磁异常区,只有少数几个地磁台位于强磁异常区;②判断1个地磁台的地磁场环境,只测量总强度（F）是不够的,必须进行三分量绝对观测,利用地磁异常场模量△T评价地磁台的地磁场环境更全面、更科学合理。 相似文献