Electric field measurements in the solar wind,bow shock,magnetosheath, magnetopause,and magnetosphere

Electric field measurements are reported at 11 magnetopause crossings that occurred during a single in-bound ISEE-1 satellite pass near a local time of 1030. In combination with magnetic field data, these measurements show the existence of electric field components tangential to the actual magnetopause in the frame of rest of the magnetopause on every crossing of the current carrying layers associated with the 11 magnetopause traversals. These tangential electric field components were oriented with respect to the magnetopause sheet currents such that there was an electrical power dissipation of between 30 and 110 W km^-2 on 10 of the 11 crossings. These results are in agreement with requirements of reconnection theories. Histograms of the normal electric field components and of the orientation, velocity, and thickness of the current carrying layer are presented. Suggestions of the existence of a parallel electric field in the magnetosheath near the magnetopause and of propagation of large amplitude waves along the magnetopause are also made.     

Energy coupling between the solar wind and the magnetosphere

This paper describes in detail how we are led to the first approximation expression for the solar wind-magnetosphere energy coupling function , which correlates well with the total energy consumption rate U _T of the magnetosphere. It is shown that is the primary factor which controls the time development of magnetospheric substorms and storms. The finding of this particular expression indicates how the solar wind couples its energy to the magnetosphere; the solar wind and the magnetosphere constitute a dynamo. In fact, the power P generated by the dynamo can be identified as by using a dimensional analysis. Furthermore, the finding of indicates that the magnetosphere is closer to a directly driven system than to an unloading system which stores the generated energy before converting it to substorm and storm energies. Therefore, the finding of and its implications have considerably advanced and improved our understanding of magnetospheric processes. The finding of has also led us to a few specific future problems in understanding relationships between solar activity and magnetospheric disturbances, such as a study of distortion of the solar current disk and the accompanying changes of . It is also pointed out that one of the first tasks in the energy coupling study is an improvement of the total energy consumption rate U _T of the magnetosphere. Specific steps to be taken in this study are suggested.     

Interaction of non-perpendicular/parallel solar wind shock waves with the earth's magnetosphere

The interaction of travelling interplanetary shock waves with the bow shock-magnetosphere system is considered. We consider the general case when the interplanetary magnetic field is oblique to the Sun-planetary axis, thus, the interplanetary shock is neither parallel nor perpendicular. We find that an ensemble of shocks are produced after the interaction for a representative range of shock Mach numbers. First, we find that the system S ₊ R _– CS _– S ₊ appears after the collision of travelling fast shock waves S ₊ (Mach number M = 2 to 7) with the bow shock. Here, S _– and R _– represent the slow shock wave and slow rarefaction wave, and C represents the contact surface. It is shown that in the presence of an interplanetary field that is inclined by 45° to the radial solar wind velocity vector, the waves R _– and S _– are weak waves and, to the first degree of approximation, the situation is similar to the previously studied normal perpendicular case. The configuration, R ₊ C _m S _– S ₊ or R ₊ C _m R _– S ₊ where C _m is the magnetopause, appears as the result of the fast shock wave's collision with the magnetopause. In this case the waves S _– and R _– are weak. The fast rarefaction wave reflected from the magnetosphere is developed similar to the case for the collision of a perpendicular shock. The shock wave intensity is varied for Mach numbers from 2 to 10. Thus, in the limits of the first approximation, the validity of the one-dimensional consideration of the nonstationary interaction of travelling interplanetary shock waves with the bow shock-magnetosphere system is proved. The appearance of the fast rarefaction wave, R ₄, decreasing the pressure on the magnetosphere of the Earth after the abrupt shock-like contraction, is proved. A possible geomagnetic effect during the global perturbation of the SSC or SI⁺ type is discussed.An invited paper presented at STIP Workshop on Shock Waves in the Solar Corona and Interplanetary Space, 15–19 June, 1980, Smolenice, Czechoslovakia.     

MHD structures, waves and turbulence in the solar wind: Observations and theories

A comprehensive overview is presented of recent observational and theoretical results on solar wind structures and fluctuations and magnetohydrodynamic waves and turbulence, with preference given to phenomena in the inner heliosphere. Emphasis is placed on the progress made in the past decade in the understanding of the nature and origin of especially small-scale, compressible and incompressible fluctuations. Turbulence models to describe the spatial transport and spectral transfer of the fluctuations in the inner heliosphere are discussed, and results from direct numerical simulations are dealt with. Intermittency of solar wind fluctuations and their statistical distributions are briefly investigated. Studies of the heating and acceleration effects of the turbulence on the background wind are critically surveyed. Finally, open questions concerning the origin, nature and evolution of the fluctuations are listed, and possible avenues and perspectives for future research are outlined.     

Magnetic reconnection,merging, and viscous interaction in the magnetosphere

Two ideas were advanced for the process of solar wind-magnetospheric interaction in the same year 1961. Dungey suggested that the interplanetary magnetic field (IMF), although weak, might determine the nature of this process by magnetic reconnection as the solar wind plasma flows across the separatrix surface which divides the IMF from the geomagnetic field. Axford and Hines pointed out that the flow inside the magnetopause is in the same sense as the magnetosheath flow and appears to be viscously coupled. Within a few years the dependence of geomagnetic activity on the IMF predicted by Dungey's mechanism was observed, and reconnection began to dominate current theories. One difficulty, that of the implied dissipation at the magnetopause, was troublesome; however, the ISEE-1/2 observations of the predicted high speed flows on several occasions was enough to convince many persons that reconnection ideas were basically correct. Several investigators found some evidence in the ISEE-3 data in the distant magnetotail for the steady-state reconnection line, as demanded by the Dungey model, in the form of a southward sense of the magnetic field through the current sheet. Here, again, there is some hard contrary evidence when the data are analyzed exactly at the cross-tail current sheet: the instantaneous values show a northward sense, even at high values of auroral activity. Coupled with the anti-Sunward plasma flow, this repudiates the steady-state Dungey model. On the other hand, it lends strong support to some kind of viscous effect through the medium of the magnetospheric boundary layer. This is not a semantic problem, as the sense of the electric field (as well as the magnetic field) is opposite for the two cases. The downfall of the reconnection model is its implicit use of frozen-field convection; this problem is obvious when the problem is viewed in three dimensions. Instead, the view is taken that the relevant process must be essentially time-dependent, three-dimensional, and localized. It is proposed that the term merging be used for this generalized timedependent form of reconnection. The merging process (whatever it is) must permit solar wind plasma to cross the magnetopause onto closed field lines of the boundary layer. Once it is there, it provides the viscous-like effect that Axford and Hines had envisaged.     

Driving mechanisms for the solar wind

In this review, we consider the central physical aspects pertinent to the acceleration of the solar wind. Special importance is placed on the high-speed streams since the properties of these structures seem to strain the various theoretical explanations the most. Heavy emphasis is also given to the observations — particularly as to what constraints they place on the theories. We also discuss certain sporadic events such as spicules, macrospicules, X-ray bright points, and outflows seen in the EUV associated with the explosive events, jets, and coronal bullets which could be of relevance to this problem.Three theoretical concepts pertaining to the solar wind acceleration process are examined — purely thermal acceleration with and without extended heating, acceleration due to Alfvén wave pressure, and diamagnetic acceleration. Emphasis is given to how well these theories meet the constraints imposed by the observations. Diamagnetism is argued to be a powerful ingredient in solar wind theory, both in the light of observed sporatic outflows seen in the chromosphere and transition region and also because of its effectiveness in increasing the flow speed and producing strong acceleration near the Sun in line with coronal hole observations.     

Magnetic holes in the solar wind and their relation to mirror-mode structures

Data obtained by the Ulysses magnetometer and solar wind analyzer have been combined to study the properties of magnetic holes in the solar wind between 1 and 5.4 AU and to 23° south latitude. Although the plasma surrounding the holes was generally stable against the mirror instability, there are indications that the holes may have been remnants of mirror mode structures created upstream of the points of observation. Those indications include: (1) For the few holes for which proton or alpha-particle pressure could be measured inside the hole, the ion thermal pressure was always greater than in the plasma adjacent to the holes. (2) The plasma surrounding many of the holes was marginally stable for the mirror mode, while the plasma environment of all the holes was significantly closer to mirror instability than was the average solar wind. (3) The plasma containing trains of closely spaced holes was closer to mirror instability than was the plasma containing isolated holes. (4) The near-hole plasma had much higher ion (ratio of thermal to magnetic pressure) than did the average solar wind.     

Magnetic field reconnection theory and the solar wind — Magnetosphere interaction: A review

This review considers the theory of the magnetic field line reconnection and its application to the problem of the interaction between the solar wind and the Earth's magnetosphere. In particular, we discuss the reconnection models by Sonnerup and by Petschek (for both incompressible and compressible plasmas, for the asymmetric and nonsteady-state cases), the magnetic field annihilation model by Parker; Syrovatsky's model of the current sheet; and Birn's and Schindler's solution for the plasma sheet structure. A review of laboratory and numerical modelling experiments is given.Results concerning the field line reconnection, combined with the peculiarities of the MHD flow, were used in investigating the solar wind flow around the magnetosphere. We found that in the presence of a frozen-in magnetic field, the flow differs significantly from that in a pure gas dynamic case; in particular, at the subsolar. part of the magnetopause a stagnation line appears (i.e., a line along which the stream lines are branching) instead of a stagnation point. The length and location of the stagnation line determine the character of the interaction of the solar wind with the Earth's magnetosphere. We have developed the theory of that interaction for a steady-state case, and compare the results of the calculations with the experimental data.In the last section of the review, we propose a qualitative model of the solar wind — the Earth's magnetosphere interaction in the nonsteady-state case on the basis of the solution of the problem of the spontaneous magnetic field line reconnection.     

IMF connection for energetic protons observed at Ulysses via mid-latitude solar wind rarefaction regions

As Ulysses moved inward and southward from mid-1992 to early 1994 we noticed the occasional occurrence of inter-events, lasting about 10 days and falling between the recurrent events, observed at proton energies of 0.48–97 MeV, associated with Corotating Interaction Regions (CIR). These inter-events were present for several sequences of two or more solar rotations at intensity levels around 1% of those of the neighbouring main events. When we compared the Ulysses events with those measured on IMP-8 at 1 AU we saw that the inter-events appeared at Ulysses after the extended emission (>10 days) of large fluxes of solar protons of the same energy that lasted at least one solar rotation at 1 AU. The inter-events fell completely within the rarefaction regions (dv/dt<0) of the recurrent solar wind streams. The interplanetary magnetic field (IMF) lines in the rarefactions map back to the narrow range of longitudes at the Sun which mark the eastern edge of the source region of the high speed stream. Thus the inter-events are propagating at mid-latitudes to Ulysses along field lines free from stream-stream interactions. They are seen in the 0.39–1.28 MeV/nucleon He, which exhibit a faster decay, but almost never in the 38–53 keV electrons. We show that the inter-events are unlikely to be accelerated by reverse shocks associated with the CIRs and that they are more likely to be accelerated by sequences of solar events and transported along the IMF in the rarefactions of the solar wind streams.     

Kinetic properties of heavy ions in the solar wind from SWICS/Ulysses

The kinetic properties of heavy ions in the solar wind are known to behave in a well organized way under most solar wind flow conditions: Their speeds are all equal and faster than that of hydrogen by about the local Alfvén speed, and their kinetic temperatures are proportional to their mass. The simplicity of these properties points to a straightforward physical interpretation; wave-particle interactions with Alfvén waves are the probable cause. With the SWICS sensor on board Ulysses, it is now possible to investigate the kinetic properties of many more ion species than before. Furthermore, the transition of Ulysses into the fast stream emanating from the south polar coronal hole since 1992 allows us to study these properties both in the slow, interstream solar wind, as well as in an unambiguously identified fast stream. We present data from SWICS/Ulysses on the dominant ions of He, C, O, Ne, and Mg. As a result we find that, both in the slow wind and in fast streams, the isotachic property is obeyed even better than it could be determined by the ICI instrument on ISEE-3. The mass proportionality ofT _kin is also shown to hold for these ions, including the newly identified C and Mg.     

立式风洞设计关键技术探索与实验研究

试验段气流速度快速调节、试验段碟形流场分布、风洞振动与试验段气流脉动的抑制是立式风洞研制的关键技术.本文简介了对这些技术的探索与设计思路,并通过分析φ0.33m立式风洞中进行的一系列性能研究试验结果,得出了相关结论.     

Interaction of the solar wind with the local interstellar medium: a theoretical perspective

The interaction of the solar wind with the local interstellar medium (LISM) is attracting renewed interest, thanks to the possibility that the Voyager spacecraft may, in the not too distant future, cross the heliospheric termination shock. This has spurred the development of increasingly sophisticated models which attempt to describe various aspects of the physics underlying the interaction of the solar wind and the LISM. A comprehensive review of the subject is presented here. This revised version was published online in August 2006 with corrections to the Cover Date.     

Voyager observations of the magnetic field, interstellar pickup ions and solar wind in the distant heliosphere

Voyagers 1 and 2 are now observing the latitudinal structure of the heliospheric magnetic field in the distant heliosphere (the legion between - 30 AU and the termination shock). Voyager 2 is observing the influence of the interstellar medium on the solar wind. The pressure of the interstellar pickup protons, measured by their contribution to pressure balanced structures, is greater than or equal to the magnetic pressure and much greater than the thermal pressures of the solar wind protons and electrons in the distant heliosphere. The solar wind speed is observed to decrease and the proton temperature increase with increasing distance from the sun. This may result from the production of pickup ions by the charge exchange process with the interstellar neutrals. The introduction of the pickup ions into the dynamics of the magnetized solar wind plasma appears to be an important new process which must be considered in future theoretical studies of the termination shock and boundary with the local interstellar medium.     

超声速湍流流场的RANS/LES混合计算方法研究

采用对接/拼接网格技术,建立了基于分区混合和基于湍流尺度混合的双重RANS/LES混合计算模型,并对环翼低速绕流、翼型跨声速绕流和球锥带凹窗外形二维超声速绕流进行了初步的数值模拟.环翼和翼型绕流计算表明,该混合模型可给出较合理的湍流宏观平均量;球锥带凹窗外形二维超声速绕流计算表明,该混合模型可得到超声速瞬态湍流脉动流场,凹窗处存在复杂的旋涡结构和波系结构,呈现较大尺度的脉动.但该模型还需要进一步的考核验证.     

PBN——民航发展新钥匙

一、不能盈利的民航不是强大的民航,PBN所能带来的强大的盈利能力将使其成为未来民航的标准在一个事物的长期发展和不断壮大的过程中,通常总是会有一些具有重要推动力的标志性技术进步,民航也不例外。例如,DC-3的出现和应用才开启了现代意义上的民航运输,因为它是第     

The european aerospace industry: a key sector at the cross-roads

The present article is the text of the speech given by Javier Alvarez Vara, on the occasion of the AECMA (European Association of Aerospace Industries) Evening Lecture, 15th September 1998 in Brussels.     

Thermoelastic problem for a physically orthotropic cylindrical shell at localized temperature

Numerical results obtained based on the equations for the general theory of physically orthotropic shells are presented. These results illustrate the influence of anisotropy for mechanical and physical characteristics of material on stressed state.     

The IMF pile-up regions near the Earth and Venus: lessons for the solar wind - Mars interaction

The Mars Global Surveyor mission has revealed that localized crustal paleomagnetic anomalies are a common feature of the Southern Hemisphere of Mars. The magnetometer measured small-scale magnetic fields associated with many individual magnetic anomalies have magnitudes ranging from hundreds to thousands nT at altitude above 120 km. That makes Mars globally different from both Venus and Earth. The data collected by Lunar Prospector near the Moon were interpreted as evidence that above regions of inferred strong surface magnetic fields on the Moon the SW flow is deflected, and a small-scale mini-magnetosphere exists under some circumstances. With a factor of 100 stronger magnetic fields at Mars and a lower SW dynamic pressure, those conditions offer the opportunity for a larger size of small `magnetospheres' which can be formed by the crustal magnetic fields. Outside the regions of the magnetic anomalies, the SW/Mars interaction is Venus-like. Thus, at Mars the distinguishing feature of the magnetic field pile-up boundary most likely varies from Venus-like to Earth-like above the crustal magnetic field regions. The observational data regarding the IMF pile-up regions near Venus and the Earth are initially reviewed. As long as the SW/Mars interaction remains like that at Venus, the IMF penetrates deep into the Martian ionosphere under the `overpressure' conditions. Results of numerical simulations and theoretical expectations regarding the temporal evolution of the IMF inside the Venus ionosphere and appearance of superthermal electrons are also reviewed and assessed.