Acceleration of low-energy magnetospheric plasma

Low-energy plasma originates in the ionosphere and is accelerated and transported to the plasma sheet and ultimately to the ring current. Using observations and basic MHD concepts, it is argued that the acceleration results basically from entrainment in flows that are rapid compared with initial ion thermal speeds. Spatial or temporal variations of such flows launch impulsive waves of the appropriate variety (acoustic, shear Alfven, or magnetosonic) to effect readjustment to the imposed boundary conditions. The most violent transient events are the earthward inductive surges of plasma in the inner plasma sheet, which launch magnetosonic waves. A number of observations strongly suggest that the induction surge waves break as they reach the inner plasma sheet or outer plasmasphere, forming transient shock waves and dissipating their energy in turbulent flows, plasma heating, and acceleration of energetic particles, forming the substorm injection boundary. Preliminary work indicates that the magnetosphere is typically configured so as to produce wave breaking near synchronous orbit, and has other interesting optical properties for MHD wave propagation as well. Exploration of magnetospheric plasma wave optics will require a better empirical knowledge of the plasma distribution.     

Ballooning perturbations in the inner magnetosphere of the Earth: Spectrum,stability and eigenmode analysis

We investigate the generation of ballooning perturbations in the inner magnetosphere of the Earth in the dipole model of the geomagnetic field taking into account ionospheric boundary conditions. The ionosphere is considered as a thin layer with finite conductivity. The eigenmode spectrum is discrete and consists of Alfvén, slow magnetosonic, flute and incompressible modes. Their interaction depends on ionospheric conductivity. The decay rate is small in noon and night sectors and large in dawn and dusk sectors. The lowest stability threshold α/γ ≈ 4.25 is determined by flute modes.     

Comparing two models of the Earth''s magnetosphere

The existence of a multiplicity of models of the Earth's magnetosphere raises the question: when are two of them equivalent in representing the real magnetosphere? The isomorphism of any two models of the Earth's magnetosphere is defined in terms of magnetic field characteristics. To assess to what degree empirical models are isomorphic with physical ones, two magnetospheres are compared: the magnetosphere of Mead and Fairfield [1975] and the physical magnetosphere proposed by Buneman, [1993]. Parameters realizing the isomorphism are found for the Buneman magnetosphere and the distribution in space of magnetic field characteristics are presented for both models.     

Laboratory experiments and space phenomena

Two types of convection were observed in the laboratory model of the magnetosphere: viscous convection and convection due to field lines common to both the magnetosphere and artificial solar wind. With a southward field component in the solar wind, convection from the Sun is observed in the polar cap, while with a large northward component, convection is directed toward the Sun. Merging of the field lines occurs in the cleft. With the southward component, a visor appears in front of the magnetosphere boundary. The decay of the visor into small magnetic structure is observed. The formation of an induced magnetosphere with a magnetic tail is shown in the experiments of the simulated conditions near non-magnetic bodies with a plasma shell (Venus, comets). A combined induced-intrinsic magnetosphere also was investigated.     

Propagation of interplanetary shocks into the Earth’s magnetosphere

This paper is devoted to the study of propagation of disturbances caused by interplanetary shocks (IPS) through the Earth’s magnetosphere. Using simultaneous observations of various fast forward shocks by different satellites in the solar wind, magnetosheath and magnetosphere from 1995 till 2002, we traced the interplanetary shocks into the Earth’s magnetosphere, we calculated the velocity of their propagation into the Earth’s magnetosphere and analyzed fronts of the disturbances. From the onset of disturbances at different satellites in the magnetosphere we obtained speed values ranging from 500 to 1300 km/s in the direction along the IP shock normal, that is in a general agreement with results of previous numerical MHD simulations. The paper discusses in detail a sequence of two events on November 9th, 2002. For the two cases we estimated the propagation speed of the IP shock caused disturbance between the dayside and nightside magnetosphere to be 590 km/s and 714–741 km/s, respectively. We partially attributed this increase to higher Alfven speed in the outer magnetosphere due to the compression of the magnetosphere as a consequence of the first event, and partially to the faster and stronger driving interplanetary shock. High-time resolution GOES magnetic field data revealed a complex structure of the compressional wave fronts at the dayside geosynchronous orbit during these events, with initial very steep parts (10 s). We discuss a few possible mechanisms of such steep front formation in the paper.     

磁层顶低混杂漂移不稳定性及等离子体幔、磁层对流的形成机制

磁层顶低混杂漂移不稳定性的理论和观测使我们可以提出一个新的磁层对流驱动模式,为了解释磁层对流的形成、磁层顶厚度等一系列磁层现象,已经提出了三种磁层模式,Dunge提出互联模式,认为行星际磁场磁力线与地磁场磁力线在磁层顶前部相互联接起来,磁层顶为一旋转间断面,太阳风粒子可直接通过磁层顶进入磁层内,虽然这一     

Formation of relativistic jets by collapsing stars to black holes

Formation of relativistic jets in the magnetosphere of collapsing stars is considered. These jets will be formed in the polar caps of magnetosphere of collapsing star, where the stellar magnetic field increases during the collapse and the charged particles are accelerated. The jets will generate non-thermal radiation. The analysis of dynamics and emission of particles in the stellar magnetosphere under collapse shows that collapsing stars can be powerful sources of relativistic jets.     

哨声波的自聚焦(Ⅱ)——当磁层对波有放大作用时的讨论

本文指出, 当磁层对波有放大作用时, 哨声波的自聚焦容易发生;当磁层对波有吸收时, 哨声波的自聚焦不容易发生.      

地球弓激波的三维模拟

利用磁流体动力学(MHD)全球模拟结果,根据弓激波的跃变特性确定出弓激波位置,建立了一个新的综合考虑了快磁声马赫数、太阳风动压、行星际磁场强度以及磁层顶曲率半径的弓激波三维位型模型.将新模型与以往模型的模拟结果进行比较发现,新的弓激波全球模型结果可靠,解决了部分现有模型不能描述弓激波三维位型的问题.研究结果表明,在行星际磁场北向时,随着快磁声马赫数的增大,弓激波日下点距离减小,但是在行星际磁场南向时,快磁声马赫数的变化对弓激波日下点距离影响不大;弓激波位型在赤道面与子午面上存在明显的不对称性,而且随着行星际磁场的转向,这种非对称性也会发生相应改变;行星际磁场南向,B_z值较小时,子午面内弓激波位型已经不是简单的抛物线,出现了明显的类似于极尖区磁层顶的凹陷变化区.      

基于对抗神经网络有限角度的磁层边界CT重构技术

对地球磁层进行软X射线成像探测是近年来磁层研究的前沿方向.由二维X射线成像图重构三维磁层边界的方法研究是与成像探测相关的重要研究课题.传统的计算机断层成像技术(CT)重构方法在图像数据很少时无法得到较好的重构结果,甚至无法重构三维结构.考虑到地球磁层空间分布范围方面的约束,当前卫星任务的轨道设计很难满足扫描角度的全方位...     

The magnetospheres of Jupiter and Saturn and their lessons for the Earth

The study of planetary magnetospheres allows us to understand processes occurring in the Earth’s magnetosphere by showing us how these processes respond under different conditions. We illustrate lessons learned about the control of the size of the magnetosphere by the dynamic pressure of the solar wind; how cold plasma is lost from magnetospheres; how free energy is generated to produce ion cyclotron waves; the role of fast neutrals in a planetary magnetosphere; the interchange instability; and reconnection in a magnetodisk. Not all information flow is from Jupiter and Saturn to Earth; some flows the other way.     

Plasma convection model and generation of longitudinal currents in the earth's magnetosphere

The aim of this paper is to investigate processes in the magnetosphere and in particular the problems of the interaction of the solar wind with the Earth's magnetic field to produce large-scale convection, electric fields and longitudinal currents in the magnetosphere. The investigation is carried out in the frame of magnetic hydrodynamics. The reason for such an approach can be found in /1/. When calculating the transfer coefficients, the Böhm approximation is used, i.e. it is considered that the plasma in the near-equatorial part of the magnetosphere (quasiplanar geometry is used in the problem for simplification) is sufficiently turbulent that the condition ωτ ≈ 1 is valid (ω is the Larmor frequency of electrons, τ is effective time between two Quasi-collisions). The main subjects of investigation in this paper are the input near the equatorial boundary layer and the plasma layer of the magnetosphere tail.     

Mercury's magnetosphere

The Mariner 10 observations of Mercury's miniature magnetosphere collected during its close encounters in 1974 and 1975 are reviewed. Subsequent data analysis, re-interpretation and theoretical modeling, often influenced by new results obtained regarding the Earth's magnetosphere, have greatly expanded our impressions of the structure and dynamics of this small magnetosphere. Of special interest are the Earth-based telescopic images of this planet's tenuous atmosphere that show great variability on time scales of tens of hours to days. Our understanding of the implied close linkage between the sputtering of neutrals into the atmosphere due to solar wind and magnetospheric ions impacting the regolith and the resultant mass loading of the magnetosphere by heavy planetary ions is quite limited due to the dearth of experimental data. However, the influence of heavy ions of planetary origin (O⁺, Na⁺, K⁺, Ca⁺ and others as yet undetected) on such basic magnetospheric processes as wave propagation, convection, and reconnection remain to be discovered by future missions. The electrodynamic aspects of the coupling between the solar wind, magnetosphere and planet are also very poorly known due to the limited nature of the measurements returned by Mariner 10 and our lack of experience with a magnetosphere that is rooted in a regolith as opposed to an ionosphere. The review concludes with a brief summary of major unsolved questions concerning this very small, yet potentially complex magnetosphere.     

Magnetospheric energetic ions from the Earth's ionosphere

In the decade and a half since the initial discovery that the Earth's own ionosphere could at times contribute measurably to the hot plasma in the magnetosphere we have made significant progress in both our knowledge and understanding of this connection. We now know that ions of ionospheric origin are found in all major regions of the magnetosphere and at its boundaries. The source region in the ionosphere and the acceleration and transport processes involved in coupling the cold ionospheric plasma to the hot magnetospheric plasma are complex and variable. We now have a good understanding of the large scale morphology of the ionospheric outflow and its distribution throughout the magnetosphere and progress is being made in the understanding of the fundamental physical processes involved. In this paper we concentrate on the large scale morphology and our understanding of the sources for ionospheric ions found in various regions of the magnetosphere and their transport.     

行星际起伏向磁层顶的输运

时间尺度为分钟数量级的太阳风速度和行星际磁场大幅度扰动实际上始终存在于行星际空间的。这些扰动一直传输到紧贴磁层边界面外侧的区域。它们在磁鞘等离子体和磁层顶的相互作用过程中可能起很重要的作用。行星际起伏中的磁场分量在通过地球弓激波时首先经历一次跳跃,然后一部分扰动被带到磁层边界面处。在边界面附近磁场扰动幅度被大大地放大了。弓激波上游的太阳风条件控制了放大因子。本文所作的数值模拟研究结果表明,如果上游有大幅度的扰动,在边界面附近就有大幅度的Alfven起伏的磁场分量。当上游磁场接近垂直于日地联线时,放大因子变得相当大,而且放大因子随上游的等离子体β值和/或Alfven马赫数的增加而增加。上游各向异性对放大因子的影响不大。在磁层边界附近存在大幅度起伏表明这里不存在稳定的片流。      

动态地球磁层的时空剖分编码

动态地球磁层时空剖分模型借鉴了广泛应用于地学大数据的地球格网模型思想，实现了面向地球磁层的动态、非规则化物理空间的多层级剖分，且剖分格网形变稳定，可以实现一定范围内地球磁层时空特性的形式化。在此基础上，对剖分得到的时空格网进行编码表达，以便于计算机存储和处理，这是构建地球磁层大规模观测数据统一管理基础时空框架的另一个关键问题。由于地球磁层特殊的时空特性，经典、单一思路的地学编码方案较难完整地反映格网间的时空关系，因此难以支持格网间的基础时空关系计算。本文融合了整数坐标编码与Morton曲线编码的基本思路，实现了对漂移壳剖分格网的高效编码方案设计，完成了动态地球磁层的时空框架构建，从而为地磁数据的高效组织和处理奠定了基础。实验证明，本文提出的编码方案编码效率较高，且可以支持高效的相邻关系计算，为动态地球磁层多源、多层级、异构的大规模观测数据的组织与计算提供了一种解决方案。      

行星际磁场北向分量触发磁层扰动的可能性

本文用典型事件和统计分析论证了行星际磁场北向分量触发地磁扰动的可能性.给出了行星际电场E_y分量对磁层大尺度对流电场E_M的耦合系数.从耦合方程出发讨论了磁层对太阳风作用的响应,证明磁层不是起半波整流器作用,从而表明经典的重联理论应有所修改.      

行星际激波导致的磁尾等离子片中ULF波动事件

磁层中的超低频（ULF）波动在太阳风和磁层之间的能量输运过程中具有重要作用.ULF波动主要发生在内磁层,且内磁层中ULF波动影响粒子的加速及沉降,而在夜侧磁层尤其是磁尾等离子片中观测到的ULF波动比较少.基于中国自主磁层探测卫星TC-1的观测数据,发现了两例行星际激波导致的磁尾中心等离子片中ULF波动事件,并发现这两例ULF事例都包含很强的环向模驻波分量,与以往THEMIS卫星报道的同类事件观测特征相符.根据ULF波的观测特征,分析了这两例ULF波动的可能触发机制.研究结果有助于深入理解磁层对行星际激波的全球响应.     

IMF北向时太阳风粒子向磁层输运的试验粒子模拟研究

以ACE卫星实时观测数据驱动的全球磁流体模拟为背景场,选取2003年10月22－24日行星际磁场（IMF）持续北向的事件,使用试验粒子方法,对太阳风粒子向磁层输运的过程进行模拟研究,分析北向IMF下太阳风粒子注入磁层过程中粒子在磁层内的空间分布和时间演化特征。IMF北向期间,进入环电流区域的粒子在晨侧区域的密度大于昏侧,且晨侧的粒子分布范围更广。背阳面磁鞘中的太阳风粒子可以通过低纬边界层进入磁层,但很难通过南北侧磁层顶进入磁层。进入磁尾的太阳风粒子聚集形成冷而密的等离子体片（CDPS）,模拟中CDPS的空间分布和密度大小与观测数据符合。在IMF长时间北向期间,磁尾的粒子数量呈现随时间增长的趋势,并存在约20 min的小幅度准周期变化和约5~6 h的较大幅度的准周期变化。      

上行离子源区卫星探测的轨道需求分析

极区从电离层到磁层的上行粒子流探测研究是空间天气建模中的重要问题,其起源和加速机制是磁层-电离层-热层耦合小卫星星座计划的主要科学目标. 磁层-电离层-热层耦合小卫星星座计划拟定由两颗磁层星和两颗电离层/热层星组成星座对极区进行联合观测. 其中,上行粒子源区附近的就位探测是电离层-热层耦合机制研究的重点,也是电离层/热层星轨道设计的关键. 根据相关空间探测计划和卫星观测结果,通过比较圆轨道和椭圆轨道两种方案,确定电离层/热层星采用椭圆轨道.