Transient phenomena in the magnetotail and their relation to substorms

Recent observations of magnetic field, plasma flow and energetic electron anisotropies in the magnetotail plasma sheet during substorms have provided strong support for the idea that a magnetospheric substorm involves the formation of a magnetic neutral line (the substorm neutral line) within the plasma sheet at X _SM — 10R _E to -25R _E. An initial effect, in the tail, of the neutral line's formation is the severance of plasma sheet field lines to form a plasmoid, i.e., a closed magnetic loop structure, that is quickly (within 5–10 min) ejected from the tail into the downstream solar wind. The plasmoid's escape leaves a thin downstream plasma sheet through which plasma and energetic particles stream continuously into the solar wind, often throughout the duration of the substorm's expansive phase. Southward oriented magnetic field threads this tailward-flowing plasma but its detection, as an identifier of the occurrence of magnetic reconnection, is made difficult by the thinness and turbulence of the downstream plasma sheet. The thinning of the plasma sheet downstream of the neutral line is observed, by satellites located anywhere but very close to the tail's midplane, as a plasma dropout. Multiple satellite observations of plasma droputs suggest that the substorm neutral line often extends across a large fraction (> ) of the tail's breadth. Near the time of substorm recovery the substorm neutral line moves quickly tailward to a more distant location, progressively inflating the closed field lines earthward of it, to reform the plasma sheet.Proceedings of the Symposium on Solar Terrestrial Physics held in Innsbruck, May–June 1978.     

The roles of direct input of energy from the solar wind and unloading of stored magnetotail energy in driving magnetospheric substorms

This paper presents the consensus arrived at by the authors with respect to the contributions to the substorm expansive phase of direct energy input from the solar wind and from energy stored in the magnetotail which is released in a sometimes unpredictable manner. Two physical processes, neither of which can be ignored, are considered to be of importance in the dispensation of the energy input from the solar wind. One of these is the driven process in which energy, supplied from the solar wind, is directly dissipated in the ionosphere with the only clearly definable delay being due to the inductance of the magnetosphere-ionosphere system. The other is the loading-unloading process in which energy from the solar wind is first stored in the magnetotail and then is suddenly released to be deposited in the ionosphere as a consequence of external changes in the interplanetary medium or internal triggering processes. Although the driven process appears to be more dominant on a statistical basis in terms of solar wind-geomagnetic activity relationships, one or the other of the two above processes may dominate for any individual cases. Moreover, the two processes may operate simultaneously during a given phase of the substorm, e.g., the magnetotail may experience loading as the driven system increases in strength. Thus, in our approach, substorms are described in terms of physical processes which we infer to be operative in the magnetosphere and the terminology of the past (e.g., phases) is related to those inferred physical processes. The pattern of substorm development in response to changes in the interplanetary medium is presented for a canonical isolated substorm.Now at Max-Planck-Institut für Physik und Astrophysik, Institut für Extraterrestrische Physik, D-8046 Garching, F.R.G.     

The magnetosheath and magnetotail of Venus

We describe the observational history and assess the current understanding of the magnetosheath and magnetotail of Venus, stressing recent developments. We make recommendations for research that can be done using existing observations, as well as desirable trajectory and instrumentation characteristics for future spacecraft missions.     

Reconnection in the magnetotail

The ion tearing mode is considered as the only mechanism capable of initiating reconnection processes in the equilibrium plasma sheet whose scale considerably exceeds the ion Larmor radius. The paper gives a brief review of linear theory of the tearing mode instability that allows the onset of its development to be determined. It is shown that the explosive growth of the tearing mode in a nonlinear stage is consistent with the dynamics of charged particle acceleration and the behaviour of the magnetic field variations and plasma flow in the magnetotail. The tail structure formed, as a result of the development of the tearing mode, is also discussed.Proceedings of the Symposium on Solar Terrestrial Physics held in Innsbruck, May–June 1978.     

Plasmas in the earth's magnetotail

An overview of the general characteristics of plasmas within the Earth's magnetotail and its environs is presented. Present knowledge of the plasmas within these regions as gained via in situ measurements provides the general theme, although observations of magnetic fields, energetic particles and plasma waves are included in the discussion. Primary plasma regimes in the magnetotail are the plasma sheet, its boundary layer, the magnetotail lobes, the boundary layer at the magnetopause and the distant magnetotail. Although great progress in our understanding of these regions is evident in the literature of the past several years, many of their features remain as exciting enigmas to be resolved by future observational and theoretical investigation.     

Wave-particle interactions and their relevance to substorms

Wave-particle effects are implicit in most models of radial diffusion and energization of Van Allen belt particles; they were explicitly used in the wave turbulence model for trapped particle precipitation and trapped flux limitations by Kennel and Petschek, Cornwall and by many others. Liemohn used wave-particle interactions to work out a theory of path-integrated whistler amplification process to explain the lack of large per-hop attenuation of multiple-hop LF whistlers.Others have now used wave-particle interactions to construct theories of ELF and VLF chorus. In the present paper we shall review the observations and some of the pertinent theoretical interpretations of wave-particle effects as they relate to substorm and storm-time phenomena. If substorms develop as a result of magnetic merging, then it seems clear that wave-particle interactions in the dissipative or so-called diffusion region of the reconnection zone may be of great importance. The plasma sheet thinning and flow towards the Earth lead inevitably to the development of particle distribution functions that contain free energy in a pitch-angle anisotropy. Such free energy can be released via plasma wave instabilities. The subsequent wave-particle interactions can result in both strong and weak diffusion of particles into loss cones with consequent precipitation fluxes into the auroral zone. Ring current proton spectra also should be unstable against various plasma instabilities with consequent ring current decay and precipitations. Wave-particle interactions must play some important roles in auroral arcs, electrojets and other phenomena related to substorms. These aspects of wave-Paticle interaction will be covered     

Source and loss processes in the magnetotail

Space Science Reviews -     

The magnetogram inversion technique: Applications to the problem of magnetospheric substorms

The magnetogram inversion technique (MIT) is based upon recordings of geomagnetic variations at the worldwide network of ground-based magnetometers. MIT ensures a calculation of a global spatial distribution of the electric field, currents and Joule heating in the ionosphere. Variant MIT-2 provides, additionally, continuous monitoring of the following parameters: Poynting vector flux from the solar wind into the magnetosphere (); power, both dissipated and accumulated in the magnetosphere; magnetic flux in the open tail; and the magnetotail length (l _T) (distance between the dayside and nightside neutral points in the Dungey model). Using MIT-2 and data of direct measurements in the solar wind, an analysis is made of a number of substorms, and a new scenario of substorms is suggested. The scenario includes the convection model, the model with a neutral line and the model of magnetosphere-ionosphere coupling (outside the current sheet), i.e., the three known models. A brief review is given of these and some other substorms models. A new element in the scenario is the strong positive feedback in the primary generator circuit, which ensures growth of the ratio = / _Aby an order of magnitude or more during the substorms. Here _Ais the Pointing vector flux in the Akasofu-Perrault approximation, i.e., without the feedback taken into account. The growth of during the substorm is caused only by the feedback effect. It is assumed that the feedback arises due to an elongation of the magnetotail, i.e., a growth of l _Tby a factor of (23) during the substorm.In the active phase of substorm, a part (the first active phase) has been identified, where the principal role in the energetics is played by the feedback mechanism and the external energy source (although the internal source plus reconnection inside the plasma sheet make a marked contribution). In the second active phase (expansion) the external generator (solar wind) is switched off, and the main role is now played by the internal energy source (the tail magnetic field and ionospheric wind energy).Models of DP-2 DP-1 transitions are also considered, as well as the magnetospheric substorm-solar flare analogy.     

Several recent findings concerning the dynamics of the Earth's magnetotail

Several recent results concerning the nature of the Earth's magnetotail are briefly reviewed. These observational findings include: (1) the three-dimensional character of the plasma sheet via a comprehensive survey of proton bulk flows, (2) a region of earthward flowing plasmas at the interfaces of the plasma sheet and magnetotail lobes during magnetic substorm recovery, and (3) the signature of electrostatic acceleration for protons within the jetting plasmas from magnetotail fireballs.Proceedings of the Symposium on Solar Terrestrial Physics held in Innsbruck, May–June 1978.     

Inductive electric fields in the magnetotail and their relation to auroral and substorm phenomena

The paper reviews the importance of inductive electric fields in explaining different magnetospheric and auroral phenomena during moderately and highly disturbed conditions. Quiet-time particle energization and temporal development of the tail structure during the substorm growth phase are explained by the presence of a large-scale electrostatic field directed from dawn to dusk over the magnetotail. Conservation of the first adiabatic invariant in the neutral sheet with a small value of the gradient in the magnetic field implies that the longitudinal energy increases at each crossing of the neutral sheet. At a certain moment, this may result in a rapid local growth of the current and in an instability that triggers the onset. During the growth phase energy is stored mainly in the magnetic field, since the energy density in the electric field is negligible compared to that of the magnetic field (ratio 1: 10⁷). An analytical model is described in which the characteristic observations of a substorm onset are taken into account. One major feature is that the triggering is confined to a small local time sector. During moderate disturbances, the induction fields in the magnetotail are stronger by at least one order of magnitude than the average cross-tail field. Temporal development of the disturbed area results in X- and O-type neutral lines. Particles near to these neutral lines are energized to over 1 MeV energies within a few seconds, due to an effective combination of linear and betatron acceleration. The rotational property of the induction field promotes energization in a restricted area with dimensions equivalent to a few Earth's radii. The model also predicts the existence of highly localized cable-type field-aligned currents appearing on the eastern and western edges of the expanding auroral bulge. It is shown that the predictions agree with satellite observations and with the data obtained from the two-dimensional instrument networks operated in Northern Europe during the International Magnetospheric Study (IMS, 1976–79).     

美国西南航适航指令事件始末

在2007年3月,美国西南航空公司(SWA)发现自己所运营的飞机不符合适航指令(AD)后将这一问题通过自愿报告系统(VDRP)向其审定管理叻公室(CMO)进行汇报,并采取补救措施.与此同时,SWA有46架与AD不符的波音737飞机又继续运营了9天.SWA的主管称其误以为CMO准许其继续运营.     

沿海地区飞机腐蚀问题及控制

本文对沿海地区飞机腐蚀因素进行了分析,并提出了几点预防措施。     

The Threshold of Civil Aviation and The Discount of Tickets

In the planned economy era, taking plane was a kind of treatment in China.There were few people who can travel by plane and even less people paid attentionto the price of tickets. Single price management system in Chinese civil aviation isthe product of that era: After the 1990s, market economic system was employed inChina. The problem of price appeared following the development and reform ofChina civil aviation, and has been the concern of more and more people and themedia. Let alone "doubl…     

知行合一,十年一剑——访金属材料定向凝固专家,南京理工大学教授陈光

( ):PST TiAl单晶获得的巨大成功与背后所做的努力工作分不开,可能经过几百次甚至上千次的讨论、构思、计算、试验和测试,您能为我们介绍一下背后所做的工作吗?陈光:每个有实用价值的重大成果一定是经历了长时间的潜心研究,正常情况下也一定得付出很多的心血.即使是灵感,也是基于长期的积累,正所谓“机遇总是青睐有准备的人”,“站在巨人的肩膀上”.     

语言测试及设计

在外语教学中，语言测试是不可缺少的环节之一。本文主要论述语言测试理论，如语言测试的目的、语言测试的类型、语言测试的标准；分析并总结了常见的语言测试项目的设计方法，如：多项选择题的设计、词汇测试的设计、完形测试的设计、阅读理解的设计、听力测试的设计、写作测试的设计；并对测试后得分的计算和分析进行解释。最后提出语言教师了解一点语言测试的知识是很有必要的。     

浅谈苏霍伊和米高扬的合并

苏霍伊和米高扬是俄罗斯历史悠久的大设计局，他们所研制的苏霍伊和米格系列飞机在世界航空界都享有盛誉。他们的合并对俄罗斯航空工业格局将产生怎样的影响？对世界航空市场以及我国航空工业将有怎样的影响？这些都是值得人们认真思考的问题。     

三轴转台结构模态分析与试验

用模态分析方法与频谱分析仪器对三轴台结构特征问题进行了试验,得出了台体结构的模态参数（频率、振型、质量、刚度和阻尼）,并与有限元方法计算值和频响测试值进行比对,为进一步作动力学分析提供了重要的数据。     

装备社会化维修保障中的相关博弈研究

鉴于"军民结合,寓军于民"战略思想的提出和现代战争的客观需要,部队装备社会化维修保障已成为必然趋势.然而军方在具体实施过程中,应如何监督管理承包商、规范和明确承包商的行为和责任以及保持或提高装备的作战性能等问题非常重要.     

航空电子系统综合技术的发展与模块化趋势

在系统阐述了航空电子综合技术及系统结构发展的基础上,全面论述了综合化及模块化的含义,指出了综合化系统及模块化在大系统结构中的层次关系。最后,提出了我国发展综合化系统应采取的策略。