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主要分析了WIND飞船2004年11月9日探测的磁云边界层引起的大尺度地球磁层活动.磁层响应主要包括以下3个方面:(1)磁云边界层内本身持续较强南向磁场驱动了一个强磁暴的主相.(2)由于磁云边界层内部较强南向磁场持续一段时间后发生向北偏转触发了一个典型磁层亚暴.文中详细分析了亚暴膨胀相发生时夜侧磁层各区域的观测现象,包括极光观测、高纬地磁湾扰、地球同步轨道无色散粒子注入现象、Pi2脉动突然增强以及等离子体片偶极化现象等.(3)磁云边界层和前面鞘区组成一个动压增强区,此动压增强区强烈压缩磁层,致使磁层顶进入地球同步轨道以内;当磁云边界层扫过磁层时,位于向阳侧地球同步轨道上的两颗GOES卫星大部分时间位于磁层磁鞘中,以致很长时间内直接暴露在太阳风中.利用Shue(1998)模型计算得到当磁云边界层扫过磁层时磁层顶日下点的位置被压缩至距地心最近距离为5.1RE,磁云边界层的强动压结构以及强间断面决定了磁云边界层对磁层的强压缩效应.强动压结构、多个强间断结构以及持续较长时间的强南向磁场是许多磁云边界层的共性,这里以此磁云边界层事件为例分析了磁云边界层的地球磁层响应. 相似文献
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2001年3月2日11:00 至11:15 UT 期间,Cluster Ⅱ在南半球极尖区晨侧附近磁鞘内探测到3个通量传输事件（简称FTEs）. 本文利用Cluster Ⅱ星簇4颗卫星观测到的磁场和等离子体资料研究了这些通量传输事件的磁场形态和粒子特征. 并利用它们探测到的空间磁场梯度资料由安培定律直接求出星簇所在区域的电流分布. 结果指出：（1）BY占优势的行星际磁场结构在磁层顶的重联可以在极尖区附近发生;（2）FTEs通量管形成初期内外总压差和磁箍缩应力不一定平衡,达到平衡有一发展过程;（3）FTEs通量管截面在L M平面内的线度约为1.89RE;（4）FTEs通量管中等离子体主要沿轴向场方向流动,整个通量管以慢于背景等离子体的速度沿磁层顶向南向尾运动;（5）FTEs通量管中不仅有轴向电流,也存在环向电流. 轴向电流基本沿轴向磁场方向流动. 轴向和环向电流在管内均呈体分布,因而轴向电流产生的环向磁场接近管心时不断减小到零,而环向电流生成的轴向场则不断增大到极值;（6）在通量管的磁鞘部分观测到磁层能量粒子流量的增强,这表明通量管通过磁层顶将磁鞘和磁层内部连通起来了. 相似文献
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主要分析了WIND飞船2004年11月9日探测的磁云边界层引起的大尺度地球磁层活动．磁层响应主要包括以下3个方面：（1）磁云边界层内本身持续较强南向磁场驱动了一个强磁暴的主相．（2）由于磁云边界层内部较强南向磁场持续一段时间后发生向北偏转触发了一个典型磁层亚暴．文中详细分析了亚暴膨胀相发生时夜侧磁层各区域的观测现象,包括极光观测、高纬地磁湾扰、地球同步轨道无色散粒子注入现荆、Pi2脉动突然增强以及等离子体片偶极化现象等．（3）磁云边界层和前面鞘区组成一个动压增强区,此动压增强区强烈压缩磁层,致使磁层顶进入地球同步轨道以内;当磁云边界层扫过磁层时,位于向阳侧地球同步轨道上的两颗GOES卫星大部分时间位于磁层磁鞘中,以致很长时间内直接暴露在太阳风中．利用Shue（1998）模型计算得到当磁云边界层扫过磁层时磁层顶日下点的位置被压缩至距地心最近距离为5．1RE,磁云边界层的强动压结构以及强间断面决定了磁云边界层对磁层的强压缩效应．强动压结构、多个强间断结构以及持续较长时间的强南向磁场是许多磁云边界层的共性,这里以此磁云边界层事件为例分析了磁云边界层的地球磁层响应． 相似文献
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磁场模式是表述空间磁场的一种有效工具,对于研究磁层大尺度电流系的发展变化和辐射带粒子具有重要意义.本文介绍了三种主要的磁层磁场模式,即经验模式、抛物面模式和事件导向模式,结合模式的原理和特点,对模式的改进情况和性能检验进行了详细论述,并对三种模式进行了对比分析.三种模式都能对暴时磁场进行动态模拟.最近的Tsyganenko模式考虑了太阳风的历史作用,每个磁场源都有自己的松弛时间尺度及驱动函数;抛物面模式A01中增加了场向电流及窄尾流效应;事件导向模式G03增加了非对称环电流和局地窄尾流片效应. 相似文献
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本文利用磁层哨声模嘶声和合声波的幅度分布模型、近赤道背景电子(能量在eV量级)的数密度分布模型和IGRF10磁场模型建立了一个高能电子(能量大于50 keV)准线性扩散模型.模型的数值结果表明,在不同的地磁条件下,等离子体层顶位置的变化改变了磁层背景电子数密度的空间分布,从而改变了哨声模嘶声对高能电子有效的投掷角扩散（损失）区域,同时也改变了哨声模合声波对高能电子有效的动量扩散（加速）区域.哨声模嘶声对电子投掷角扩散区域的变化和RRES卫星探测到的高能电子的槽区变化是一致的,而合声波对电子的动量扩散区域的变化和卫星探测到外辐射带的变化相同.这种对应关系说明：在不同的地磁条件下,哨声模波对高能电子扩散区域的变化是造成高能电子槽区和外辐射带的空间位置和大小变化的一个重要因素.在一些强磁暴期间,由于嘶声对部分能量范围电子的投掷角扩散作用消失,这些电子的槽区也随之消失,从而使内外辐射带连接在一起. 相似文献
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利用全球磁流体力学(MHD)的模拟结果,研究了太阳风压力系数与上游太阳风参数和日下点磁层顶张角的相关性.在识别出日下点附近磁层顶位置后,通过拟合得到日下点附近的磁层顶张角.在考虑上游太阳风中的磁压和热压以及磁层顶外侧的太阳风动压的情况下,计算了太阳风压力系数.通过分析行星际磁场不同方向时太阳风动压在日地连线上与磁压和热压的转化关系,详细研究了太阳风参数和日下点磁层顶张角对太阳风压力系数的影响,得到以下相关结论:(1) 在北向行星际磁场较大(Bz≥5 nT)时,磁层顶外侧磁压占主导,南向行星际磁场时磁层顶外侧热压占主导;(2) 太阳风压力系数随着行星际磁场的增大而增大,随着行星际磁场时钟角的增大而减小;并且在行星际磁场大小和其他太阳风条件相同时,北向行星际磁场时的太阳风压力系数要大于南向行星际磁场时的;北向行星际磁场时,太阳风压力系数随着太阳风动压的增大而减小,南向行星际磁场时,太阳风压力系数随着太阳风动压的增大而增大;以上结论是对观测结果的扩展;(3) 最后,我们还发现太阳风压力系数随着日下点磁层顶张角的增大而增大. 相似文献
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本文根据苏黎世天文台太阳黑子11年周期资料和太阳黑子磁场磁性变化周期特征,构建了太阳黑子磁场磁性指数MI(Magnetic Index)时间序列.分析表明：太阳活动磁性周期平均长度为222年,但是每个周期长度是不相等的;多数情况周期短时磁性指数较大,对应太阳活动水平强;周期变长时磁性指数较小,对应太阳活动水平较弱;太阳黑子磁场磁性指数序列也具有80～90年的世纪周期. 进一步研究指出,太阳黑子磁场磁性指数曲线由极小值升至极大值时期,太阳磁场南向,行星际磁场磁力线与地磁场磁力线重联,此时磁层为开磁层,太阳风将携带大量等离子体从向阳面进入地球磁层,从而使输入的动量、能量和物质大幅度增加,与北半球对流层增温时期对应;太阳黑子磁场磁性指数曲线由极大值下降至极小值时期,太阳磁场北向,与磁层顶地磁场同向,行星际磁场不会与地磁场发生重联,此时磁层为闭磁层,这种情况下,只有少数带电粒子能够穿越磁力线进入地球磁层,与北半球对流层降温时期对应. 相似文献
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用二维磁流体力学数值模拟研究了磁层顶的磁场湍动重联．提出了一个新的磁场湍动重联模型．数值模拟表明，如果磁层顶是一个开放系统并同时存在磁场剪切和流场剪切，当雷诺数和磁雷诺数超过某临界数值时，磁场重联具有很强的湍动特性，可产生许多不同尺度的磁岛和涡旋结构．随着雷诺数和磁雷诺数的增大和减小，大尺度结构能破碎成中小尺度结构，小尺度结构也能合并成大中尺度结构．湍动重联是涡旋诱发重联在一定条件下的过渡．依据本文的模拟结果，我们预言：磁层预可发生准定常重联、瞬时局地重联和湍动重联等多种重联过程；大中小不同尺度的结构都可以存在于磁层顶；湍动重联及其所产生的中小尺度结构在太阳风－磁层的能量、动量和质量耦合过程中可起重要作用． 相似文献
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基于CM4模型的中国大陆地区地磁场时空分布特征分析 总被引：1，自引：1，他引：0
本文利用第四代地磁场综合模型（Comprehensive Model 4,CM4）,计算了1982-2001年中国大陆地区同一经度链和同一纬度链上地磁台站的磁层源磁场及其感应场、电离层源磁场及其感应场的地磁北向分量X、东向分量Y、垂直分量Z的模型值,分析了各场源磁场随时间和空间的变化特征。结果表明:在时间上,经度链和纬度链台站的磁层源磁场及其感应场均呈现出11年和27天周期性变化。电离层源磁场及其感应场具有明显的季节变化,不同年份相同季节变化形态一致但幅度不同。在空间分布上,经度链和纬度链台站磁层源磁场及其感应场的年变化幅度呈现出不同变化特征,电离层源磁场及其感应场在经度链上变化特征不同,而纬度链台站的数值基本一致。日变化分析显示,磁静日和磁扰日期间,模型数据与台站实测数据变化一致性较好,相关性较高。 相似文献
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G. S. Lakhina 《Surveys in Geophysics》1994,15(6):703-754
Electromagnetic fields and currents connect various regions of the earth's near space environment extending upto the magnetopause. Realization of this fact has lead to the concept of Global Electric Circuit (GEC) to describe the electromagnetic environment of the earth's atmosphere. Solar wind - magnetosphere - ionosphere coupling forms a vital component of GEC. Magnetospheric substorms represent a global interaction between the solar wind, the magetosphere, and the ionosphere. This article gives an overview of the solar wind - magnetosphere- ionosphere coupling processes with emphasis on the nonlinear particle dynamics in the magnetotail. Those aspects of the substorm processes which involve the chaotic dynamics are highlighted. Various methods based on nonlinear particle dynamics, linear prediction filtering techniques, phase space reconstruction techniques, and dynamical anologue models of geomagnetic activity are reviewed. It is shown that the solar wind- magnetosphere - ionosphere system behaves as a strongly coupled nonlinear dynamical system which could be driven from regular to chaotic behavior with low dimensionality when the solar wind forcing is strong enough. 相似文献
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A. V. Guglielmi 《Izvestiya Physics of the Solid Earth》2009,45(9):740-743
The paper is dedicated to the 70th anniversary of the formulation of the Leontovich impedance boundary condition. This boundary
condition is applied in geophysics for sounding of the lithosphere and diagnostics of the magnetosphere by electromagnetic
waves. The use of the Leontovich condition is shown to open new possibilities for investigating the anharmonicity of MHD oscillations
of the magnetosphere. The differential impedance equation, which is derived with the aid of the Leontovich boundary condition,
can prove useful in the investigation of the electroconductivity of the lithosphere by the method of inductive sounding. It
is shown within the framework of a simple model that the method of the Leontovich parabolic equation makes it possible to
find a correction to the Leontovich boundary condition caused by the fact that, in general, the relation between the horizontal
components of an electromagnetic field is not local. It is shown that the anharmonicity of MHD oscillations of the magnetosphere
coupled with the nonlocality of the boundary condition on the Earth’s surface can lead to an apparent nonlinearity of the
surface impedance calculated in accordance with the classical technique of magnetotelluric sounding. 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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《Journal of Atmospheric and Solar》2005,67(6):637-658
We review our understanding of the electrical properties of the lower and upper atmosphere along with various possible sources of the electromagnetic energy near and far above the Earth's surface. The transport of electromagnetic energy from the atmosphere to the ionosphere and then to the magnetosphere and back to the Earth's surface via ionosphere and lower atmosphere is discussed. The electromagnetic coupling of various regions is also discussed. 相似文献
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Synchronism in geophysical events became the focus of the research in the second half of the last century when the study of this subject was almost simultaneously launched in the former Soviet Union and the United States. Interest in this issue has recently risen after a 20-year hiatus. The impetus was provided by the successful application of the synchronous detection technique to analyzing vast volumes of digital data on the electromagnetic waves in the magnetosphere and on the earthquakes. These studies revealed signs of the strictly periodic synchronous influence of the technosphere on the regime of electromagnetic oscillations in cosmic plasma and on seismic activity. The phenomenon of synchronism between the electromagnetic and seismic events manifests itself in the form of the so-called hour-mark effect and the weekend effect. The hourmark effect shows itself in the 24th, 48th, and 96th harmonics, and the weekend effect, in the 7th subharmonic of the circadian rhythm. The both effects indicate that the technosphere has a nontrivial impact on the magnetosphere and lithosphere. The present review aims to introduce the morphology of the phenomenon and to focus the attention of researchers on the physical interpretation of the effects of synchronism, which is a challenging problem. Both the fundamental and practical value of the problem is analyzed. In particular, it is hypothesized that the study of the anthropogenic modulation of the natural wave processes will promote the development of energy saving technologies. 相似文献
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The works in the alternative direction of magnetospheric studies are reviewed. In contrast to the traditional approach, where the basis process is magnetic field line reconnection, transformation of kinetic energy into electromagnetic one at the bow shock front is the basis process in the proposed approach. It has been indicated that this new paradigm makes it possible to overcome the main difficulties that remained within the scope of the previous paradigm. It has been briefly demonstrated how several following processes and phenomena are explained within the scope of the new approach: (1) transformation of the solar wind kinetic energy into the electromagnetic energy; (2) electromagnetic energy transfer into the magnetosphere; (3) organization of the system of bulk currents, formation of field-aligned currents from the magnetosphere, and compatibility of these currents with the ionospheric current systems; (4) shape, value, and dynamics of the particle precipitation auroral regions; and (5) substorm expansion (auroral breakup). Other possibilities of the new approach and paradigm replacement consequences are briefly considered. 相似文献
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Regions of the detection of electromagnetic ion-cyclotron (EMIC) waves on the THEMIS satellites near the equatorial plane and the precipitation of energetic protons on POES low Earth orbiting satellites are compared with the magnetospheric magnetic field model. It is confirmed that low Earth orbiting satellites detect the precipitation of energetic protons in the regon associated with observations of EMIC waves in the magnetosphere. This is consistent with the idea that protons are scattered in the loss cone as a result of ioncyclotron interaction. Thus, observations of fluxes of energetic protons in low Earth orbits can be used to monitor ion-cyclotron instability regions in the magnetosphere. Simultaneous observations at high and low Earth orbits contribute to the construction of a spatiotemporal pattern of the interaction region of EMIC waves and energetic protons. In addition, it is shown that proton precipitation associated with EMIC waves can cause errors in determining the latitude of the isotropic boundary (the equatorial boundary of isotropic fluxes of energetic protons), which is an indicator of the configuration of the magnetic field in the magnetosphere. 相似文献
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《Journal of Atmospheric and Solar》2003,65(10):1161-1167
The ultra-low-frequency (ULF) geomagnetic pulsations observed at two nearly conjugate mid-latitude sites are examined to study their spatial structure and polarization, and learn about the role of ionospheric conductivity in forming their ground signatures. The data of 1999–2002 from Antarctica and New England (L of 2.4) are compared with the numerical results obtained in a simple plane model of ULF wave propagation through the ionosphere and atmosphere. The multi-layered model environment includes an anisotropic and parametrically time-dependent ionosphere, a uniform magnetosphere and a conducting Earth, all placed in a tilted geomagnetic field. The measured diurnal and seasonal variations in the orientation angle of the polarization ellipse are interpreted as effects of hydromagnetic wave propagation through the ionosphere and conversion to an electromagnetic field below. Essentially, the phase, amplitude and polarization of ULF waves observed at the ground are controlled by the wave's spatial structure in the magnetosphere and ionospheric transverse conductivities. The differences shown by the characteristics of simultaneous pulsations in conjugate areas arise mainly from different local ionospheric conditions, while the source waves of the pulsations are common to both sites. 相似文献
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The theory of plasma density redistribution and polar wind acceleration acceleration under the affect on the magnetosphere of the ponderomotive forces induced by the ultra-low frequency electromagnetic waves is presented. Our attention is focused mainly on the important question about the necessity of experimental verification of fairly certain theoretical predictions. It is pointed out that experimental validation is not only necessary for the development of the theory but also for replenishing the knowledge about the structure and dynamics of the near-Earth space. An original method for indirect verification is presented. The idea of this method is based on the dependence of the foreshock locations on the orientation of the field lines of the interplanetary magnetic field (IMF) in front of the magnetosphere relative to the plane of the geomagnetic equator. 相似文献