Stimulation of VLF amplification in the magnetosphere

Among the various plasma instabilities that exert influence on the dynamic equilibrium state of the magnetosphere, the cyclotron-resonance interaction appears to be the most accessible to artificial stimulation. The strength of the interaction is sensitive to both the background magnetoplasma parameters and the hot energetic particle distribution. Thus, proper modification of one or more conditions can induce significant wave amplification at the expense of hot plasma energy density. Several methods of hot and cold plasma injection have been investigated with the linear theory to assess their effectiveness as a means of stimulating amplification.Only the interaction of VLF waves (3–30 kHz) with hot electrons (0.1–100 keV) is treated here. The injection of a dense jet of barium that travels upward along the geomagnetic field causes appreciable amplification when the jet is within 30° of the geomagnetic equator. Injection of a geosynchronous lithium cloud stimulates amplification of both VLF and ULF waves, but the magnitude depends critically on the state of geomagnetic activity. Conventional hot electron beams may also amplify narrow frequency bands, but the net wave energy is severely limited by the beam energy.Although the cyclotron-resonance is recognized as a dominant interaction in magnetospheric dynamics, its properties have never been confirmed quantitatively by appropriate spacecraft experiments. Controlled injections would provide important insight into this fundamental process because the induced amplification has a well-defined signature.     

Geomagnetically trapped radiation

This review covers the major developments in radiation-belt phenomenology of the past four years (1970–1973). This has been a period characterized by consolidation and refinement of ideas and measurements related to geomagnetically trapped particles. Significant progress has been made in understanding ion and electron pitch-angle distributions within the context of radial diffusion and pitch-angle diffusion, respectively. Comparison of alpha-particle and proton distributions has helped to clarify the relative strengths of known radial-diffusion mechanisms. Careful measurements have indicated the directional flux of cosmic-ray-albedo neutrons, which constitute (through beta decay) a major source of high-energy ( 20 MeV) inner-belt protons. Inclusion of radial-diffusion and geomagnetic-secular effects has brought the theory of the inner proton belt into reasonable agreement with observation. At very lowL values (L 1.2) atmospheric collisions have been found to facilitate the radial transport of 40 keV protons and 2 MeV electrons. The plasmapause has been identified as an important boundary for plasma instabilities (wave-particle interactions) that lead to particle precipitation and red-arc excitation. Suggestions have followed for artificially simulating such plasmaspheric effects by magnetospheric injection of cold barium or lithium plasma.     

Multi-experiment determination of plasma density and temperature

An attempt has been made to combine data from five instruments on GEOS-1 in order to determine the characteristics of the ambient cold plasma, assess the effects of spacecraft sheaths on the different techniques and establish cross calibration criteria. In addition to measuring plasma density and temperature it is necessary to consider the influence of satellite potential and motion, ionic composition, ion drifts (electric fields), electrons emitted from spacecraft surfaces and any consequent departures from isotropy or Maxwellian distribution.9 October 1977 was selected for the study, the orbit covers a range of L-values between 3.5 and 7.5 giving outbound and inbound plasmapause crossings with plasma densities spanning more than two orders of magnitude. Eclipse data from 7 February 1978 is used to determine the influence of photoelectron emission.Three techniques — active sounding of the plasma frequency resonance (S-301), a mutual impedance measurement (S-304) and DC electric field probe determination of floating potential (S-300) — utilize the long boom sensors in either AC or DC modes. Electrons and ions are measured directly by electrostatic analysers (S-302), mounted on one short radial boom. On the day chosen for study here ions are predominantly protons as determined by the body mounted ion composition experiment (S-303).The techniques using the 20 m long booms agree well in determining density whereas the short boom and body mounted ion detectors are seriously compromised when satellite potential becomes several volts positive. Measurements of satellite potential and plasma temperature agree within 20% among the several instruments making these measurements. Data obtained during the transition from eclipse to sunlight conditions show no discontinuity in the long boom instruments caused by the sudden appearance of photoelectrons.     

Analyses of techniques for measuring DC and AC electric fields in the magnetosphere

Methods for measuring the amplitudes and directions of DC electric fields and the directions, power spectra, and dispersion relations of AC electric fields in the magnetosphere are discussed with emphasis on their applicability in various regimes of the magnetospheric plasma. The two classes of techniques that are discussed are measurement of the bulk flow of the plasma and the potential difference between pairs of separated conductors. The plasma bulk flow discussion includes measurements by ionospheric radar backscatter, whistler mode wave propagation, energetic or thermal particle trajectories, artificial ion cloud motion, probe measurements of bulk flow, vehicle wake analyses, effects of bulk flow on the coupling of antennas, and the bulk flow of an artificial electron beam.     

What auroral electron and ion beams tell us about magnetosphere-ionosphere coupling

The electron and ion beams which have been detected on many rockets and satellites are of particular interest because beam particles carry information about both the ionosphere and the magnetosphere out to the distant tail. Stability analyses have shown that even the most dramatic beams have evolved until the particle distribution functions are only weakly unstable. The shortest plasma wave growth lengths in the auroral region are usually comparable to the size of an arc. The resulting clearest electron beams generally are relatively minor features of distribution functions which are dominated by plateaus, loss cones, broad or stretched out field aligned features, and hot or cold isotropic components. The true electron beams therefore represent a small fraction of the total electron number density. Ion beams carry a much larger fraction of all ions, but also are only weakly unstable. The electron beams seen at low altitudes can drive whistlers (both electromagnetic and electrostatic, including lower hybrid waves) and upper hybrid waves, which may be particularly intense near electron gyroharmonics. Ion beams can drive low frequency electromagnetic waves that are related to gyrofrequencies of several ion species as well as ion acoustic and electrostatic ion cyclotron waves. These latter waves can be driven both by the drift of ion beams relative to cold stationary ions and by the drift of electrons relative to either stationary or drifting ions. Abrupt changes or boundaries in the electron and ion velocity space distribution functions (e.g. beams and loss cones) have been analyzed to provide information about the plasma source, acceleration process, and regions of strong wave-particle interactions. Fluid analyses have shown that upgoing ion beams carry a great deal of momentum flux from the ionosphere. This aspect of ion beams is analyzed by treating the entire acceleration region as a black box, and determining the forces that must be applied to support the upgoing beams. This force could be provided by moderate energy (10's of eV) electrons which are heated near the lower border of the acceleration region. It is difficult to use standard particle detectors to measure the particles which carry electric current in much of the magnetosphere. Such measurements may be relatively easy within upgoing ion beams because there is some evidence that few of the hard-to-measure cold plasma particles are present. Therefore, ion beam regions may be good places to study fluid or MHD properties of magnetospheric plasmas, including the identification of current carriers, a study of current continuity, and some aspects of the substorm and particle energization processes. Finally, some of the experimental results which would be helpful in an analysis of several magnetospheric problems are summarized.     

Performance and characteristics of large lithium ion cells with lowtemperature electrolyte

The US Army and Saft have developed a large lithium ion battery to replace the BE-622 silver zinc battery for application for the ITAS System. The Army discovered that using the 1M LiPF6 1EC:1EMC:1DMC electrolyte can meet ITAS low temperature requirements at -40°C and still provide 71% of the room temperature capacity. This is about 40% better than silver zinc at low temperature     

The near-Earth plasma sheet: An AMPTE/IRM perspective

During the last five years, statistical studies using plasma measurements made by the AMPTE/IRM satellite have lead to a better understanding of the structure and dynamics of the near-Earth plasma sheet between about 10 and 20R _E. The most notable new findings are: (1) the adiabatic non-isentropic behavior of the tail plasma during quiet times; (2) the strong non-adiabatic heating of ions and electrons during substorms and the strong coupling of the ion and electron temperature withT _i/T_i7; and (3) the high-speed flow bursts which carry most of the tail plasma transport. Moreover, it became clear that it is the central plasma sheet, and not the plasma sheet boundary layer, which is most affected by substorm activity.     

Magnetic Cleanliness Program Under Control of Electromagnetic Compatibility for the SELENE (Kaguya) Spacecraft

To achieve the scientific objectives related to the lunar magnetic field measurements in a polar orbit at an altitude of 100 km, strict electromagnetic compatibility (EMC) requirements were applied to all components and subsystems of the SELENE (Kaguya) spacecraft. The magnetic cleanliness program was defined as one of the EMC control procedures, and magnetic tests were carried out for most of the engineering and flight models. The EMC performance of all components was systematically controlled and examined through a series of EMC tests. As a result, the Kaguya spacecraft was made to be very clean, magnetically. Hence reliable scientific data related to the magnetic field around the Moon were obtained by the LMAG (Lunar MAGnetometer) and the PACE (Plasma energy Angle and Composition Experiment) onboard the Kaguya spacecraft. These data have been available for lunar science use since November 2009.     

Waves and wave-particle interactions in the magnetosphere: A review

Recent space observations of waves, both electromagnetic and electrostatic, are reviewed and the role which they can play in the dynamics of magnetospheric particles is stressed. Wave particle interactions (WPI) in the exo- and intra-plasmaspheric media depend on the exact process of particle injection under the influence of magnetospheric electric fields, and on the spatial distribution of the cold plasma particles; these two aspects of the problem are studied to some extent. The concepts of optimum cold plasma density, critical energy, limiting flux, marginal stability, steady-state equilibrium are critically discussed. The non-linear aspects — both experimental and theoretical — of WPI's are reviewed and a special section is devoted to active experiments in space. An attempt is made to outline which kind of experiments could be made at high-latitudes, in conjunction with IMS spacecrafts, in order to arrive at a better understanding of magnetospheric processes involving waves and particles.Paper presented at the Esro Symposium on European Sounding Rocket and Scientific Balloon Activity at High Latitudes with Emphasis on the International Magnetospheric Study (Örenäs Slott, Sweden, 1974).     

基于SP+模型的航空锂离子电池组优化技术研究

随着多电飞机技术与锂离子电池技术的发展,锂离子电池已经广泛应用于航空领域,除作为应急电池外,越来越多地作为动力电池应用于飞机。因飞机对锂离子电池组质量、体积等特性具有很高的要求,需要对其进行优化设计,而采用基于模型的方法开展优化设计可以有效减少成本并缩短周期。由于SP+电化学模型能够准确反映锂离子电池的工作机理,同时具有精度高、计算简便等特点,因此文中采用SP+模型构建锂离子电池组模型并进行了验证。同时,以典型的用电工况为例,开展了航空锂电池组的优化设计,实现了对锂离子电池组质量与体积的优化。     

The plasma instrumentation for the Galileo Mission

The plasma instrumentation (PLS) for the Galileo Mission comprises a nested set of four spherical-plate electrostatic analyzers and three miniature, magnetic mass spectrometers. The three-dimensional velocity distributions of positive ions and electrons, separately, are determined for the energy-per-unit charge (E/Q) range of 0.9 V to 52 kV. A large fraction of the 4-steradian solid angle for charged particle velocity vectors is sampled by means of the fan-shaped field-of-view of 160°, multiple sensors, and the rotation of the spacecraft spinning section. The fields-of-view of the three mass spectrometers are respectively directed perpendicular and nearly parallel and anti-parallel to the spin axis of the spacecraft. These mass spectrometers are used to identify the composition of the positive ion plasmas, e.g., H⁺, O⁺, Na⁺, and S⁺, in the Jovian magnetosphere. The energy range of these three mass spectrometers is dependent upon the species. The maximum temporal resolutions of the instrument for determining the energy (E/Q) spectra of charged particles and mass (M/Q) composition of positive ion plasmas are 0.5 s. Three-dimensional velocity distributions of electrons and positive ions require a minimum sampling time of 20 s, which is slightly longer than the spacecraft rotation period. The two instrument microprocessors provide the capability of inflight implementation of operational modes by ground-command that are tailored for specific plasma regimes, e.g., magnetosheath, plasma sheet, cold and hot tori, and satellite wakes, and that can be improved upon as acquired knowledge increases during the tour of the Jovian magnetosphere. Because the instrument is specifically designed for measurements in the environs of Jupiter with the advantages of previous surveys with the Voyager spacecraft, first determinations of many plasma phenomena can be expected. These observational objectives include field-aligned currents, three-dimensional ion bulk flows, pickup ions from the Galilean satellites, the spatial distribution of plasmas throughout most of the magnetosphere and including the magnetotail, and ion and electron flows to and from the Jovian ionosphere.     

Expected charge states of energetic ions in the magnetosphere

This paper reviews major developments in our understanding of the physics of energetic heavy ions in the Earth's plasma environment during the past four years (1974–1977). Emphasis is placed on processes that influence or are influenced by the ion charge states. This has been a period of growing awareness of the important role heavy ions play in space plasmas. Large fluxes of helium ions and even heavier ions have been observed at the geostationary altitude and in the heart of the radiation belts. Such ions have also been observed on low latitude rockets and satellites, and oxygen ion precipitation exceeding that of protons has been reported. In the outer parts of the Earth's plasma envelope there is mounting evidence for significant fluxes of heavy ions: in the magnetotail, the magnetosheath and in the polar cusp regions. In the inner magnetosphere there is a limited theoretical understanding of equatorially mirroring ions, but generally only radial diffusion at one pitch angle and pitch angle diffusion at one L- shell have been studied; for ions the coupled equations are yet unsolved even for the simplest case of only one charge state (protons). Theoretical modeling of the charge state structures of geophysical heavy ion populations is in part frustrated by the lack of adequate laboratory measurements of the pertinent charge exchange cross sections. A first attempt has, however, been made to treat the charge state transformation processes in the radiation belts for equatorially mirroring atomic oxygen ions. Wave-particle interactions in the magnetosphere become much more complex in multi component and multi charge state plasmas where hybrid resonances and wave-particle interaction induced non-linear species-species coupling could be important. Heavy ion plasma physics in the Earth's magnetosphere and in the magnetospheres of other planets should be a field of fruitful study for both experimentalists and theoreticians in the years ahead.Proceedings of the Symposium on Solar Terrestrial Physics held in Innsbruck, May–June 1978.     

Interstellar Matter and the Boundary Conditions of the Heliosphere

The interstellar cloud surrounding the solar system regulates the galactic environment of the Sun, and determines the boundary conditions of the heliosphere. Both the Sun and interstellar clouds move through space, so these boundary conditions change with time. Data and theoretical models now support densities in the cloud surrounding the solar system of n(H0)=0.22±0.06 cm−3, and n(e−)∼0.1 cm−3, with larger values allowed for n(H0) by radiative transfer considerations. Ulysses and Extreme Ultraviolet Explorer satellite He0 data yield a cloud temperature of 6400 K. Nearby interstellar gas appears to be structured and inhomogeneous. The interstellar gas in the Local Fluff cloud complex exhibits elemental abundance patterns in which refractory elements are enhanced over the depleted abundances found in cold disk gas. Within a few parsecs of the Sun, inconclusive evidence for factors of 2–5 variation in Mg+ and Fe+ gas phase abundances is found, providing evidence for variable grain destruction. In principle, photoionization calculations for the surrounding cloud can be compared with elemental abundances found in the pickup ion and anomalous cosmic-ray populations to model cloud properties, including ionization, reference abundances, and radiation field. Observations of the hydrogen pile up at the nose of the heliosphere are consistent with a barely subsonic motion of the heliosphere with respect to the surrounding interstellar cloud. Uncertainties on the velocity vector of the cloud that surrounds the solar system indicate that it is uncertain as to whether the Sun and α Cen are or are not immersed in the same interstellar cloud. This revised version was published online in June 2006 with corrections to the Cover Date.     

低温等离子体辅助加工综述

随着航空航天、国防科技、能源等领域的快速发展,具有优良机械性能的高强度合金材料及复合材料得到广泛应用,实现这些材料的高效精密低损伤加工具有重要意义。低温等离子体富含活性粒子,能有效改善材料的可切削性,且较易产生、维持和控制,已被广泛应用于难加工材料的辅助加工过程中。在介绍低温等离子体基本特性及分类的基础上,结合国内外低温等离子体辅助加工技术的研究现状,以表面粗糙度、材料去除率、表面损伤、切削力等参数为评价指标,分别阐述了等离子体熔射成形技术、等离子体加热辅助切削技术、冷等离子体射流辅助抛光技术、冷等离子体射流辅助切削技术等的作用机理及效果,并对其发展趋势进行了展望。     

Diagnostic and modelling investigation on the ion acceleration and plasma throttling effects in a dual-emitter hollow cathode micro-thruster

Hollow cathode discharges are widely used as neutralizers for the electric propulsion systems and recently developed into micro-thrusters for the small satellites. In this work, a dual-emitter hollow cathode thruster is developed, which can be operated in two different modes—the neutralizer mode and the micro-thruster mode. For characterizing this kind of new device, the Langmuir probe, Faraday probe, and retarding potential analyzer are used to determine the electron temperature, electron density, ion flux, and ion energy distribution function. The operating parameters, including the thrust, and specific impulse, are also measured. A two-dimensional self-consistent extended fluid model is employed to calculate the spatial distribution of plasma parameters and the fluid field of electrons in the region around the emitters. By comparing the diagnostic and modelling results, it is found that the change in the electric field and ionization zone is the essential reason for the different performances of the device in the neutralizer and micro-thruster modes. Variation in the electric field leads to an ion acceleration effect in the micro-thruster mode; moving of the ionization zone raises the plasma pressure in the orifice region of the hollow cathode, and thus leads to enhanced plasma throttling and gas expanding effects. By analyzing the above mechanisms, the possible methods for improving this kind of hollow cathode micro-thruster are discussed.     

Modelling Electrostatic Sheath Effects on Swarm Electric Field Instrument Measurements

The Electric Field Instrument (EFI) was designed to measure ionospheric ion flow velocities, temperatures and distribution functions at the ram face of the European Space Agency’s Swarm spacecraft. These flow velocities, combined with the known orbital velocity of the satellite and local magnetic field, will be used to infer local electric fields from the relation E=?v×B. EFI is among a class of many particle sensors and flow meters mounted on satellites to monitor in situ plasma conditions. The interpretation of the measurements made with EFI and similar sensors relies on a spacecraft sheath model. A common approach, valid in the relatively cold and dense ionospheric plasma, is to assume a potential drop in a thin sheath through which particle deflection and energisation can be calculated analytically. In such models, sheath effects only depend on the spacecraft floating potential, and on the angle of incidence of particles with respect to the normal to the surface. Corrections to measurements are therefore local as they do not depend on the geometry of nearby objects. In an actual plasma, satellites are surrounded by electrostatic sheaths with a finite thickness. As a result, local corrections to particle distribution functions can only be seen as an approximation. A correct interpretation of measured particle fluxes or particle distribution functions must, at least in principle, account for the extent and shape of the sheath in the vicinity of the measuring instrument. This in turn requires a careful analysis of the interaction of the satellite with the surrounding plasma, while accounting for detailed aspects of the geometry, as well as for several physical effects. In this paper, the validity of the thin sheath model is tested by comparing its predictions with detailed PIC (Particle In Cell) calculations of satellite-plasma interaction. Deviations attributed to sheath finite thickness effects are calculated for EFI measurements, with representative plasma parameters encountered along the planned Swarm orbit. Finite thickness effects of the plasma sheaths are found to induce EFI velocity measurement errors not exceeding 37 m/s, with larger errors occurring in plasmas that are simultaneously tenuous (10⁹ m^?3 or lower) and warm (0.5 eV or higher).     

EMI滤波器控制传导干扰实验与分析

应用理论分析和实验总结出来的关于共模和差模传导干扰信号的分布规律,分析电子设备电源线上存在的干扰信号的特点,试用不同网络结构的电磁干扰(EMI)滤波器来控制电子设备在在的传导干扰电平,使之符合有关电磁兼容性(EMC)标准规定的极限值为例,说明EMI滤波器设计和应用中碰到的某些实际问题,对指导用EMI滤波器来解决电子设备存在的电磁干扰和进行EMC试验很有实际意义。     

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.     

掺铥光纤放大器对双单频激光放大的特性分析

建立了掺铥(Tm3+)光纤放大器对双单频激光放大的理论模型,对比分析了前向抽运方式下,双单频放大和单频放大时泵浦功率、信号功率、受激布里渊散射(SBS)功率,以及温度情况的不同.理论仿真了Tm3+离子掺杂浓度、光纤纤芯的有效面积和换热系数对双单频放大的影响.适当的掺杂浓度,可以有效地缩小放大器中光纤长度,减弱因过长的光纤对激光的损耗,还可以提高放大器的量子效率;选取较小的光纤的纤芯有效面积,可以获得较高的信号功率输出和较小的SBS功率;较小的换热系数可以降低SBS功率,从而有效抑制SBS效应.     

The Cassini Ion and Neutral Mass Spectrometer (INMS) Investigation

The Cassini Ion and Neutral Mass Spectrometer (INMS) investigation will determine the mass composition and number densities of neutral species and low-energy ions in key regions of the Saturn system. The primary focus of the INMS investigation is on the composition and structure of Titan’s upper atmosphere and its interaction with Saturn’s magnetospheric plasma. Of particular interest is the high-altitude region, between 900 and 1000 km, where the methane and nitrogen photochemistry is initiated that leads to the creation of complex hydrocarbons and nitriles that may eventually precipitate onto the moon’s surface to form hydrocarbon–nitrile lakes or oceans. The investigation is also focused on the neutral and plasma environments of Saturn’s ring system and icy moons and on the identification of positive ions and neutral species in Saturn’s inner magnetosphere. Measurement of material sputtered from the satellites and the rings by magnetospheric charged particle and micrometeorite bombardment is expected to provide information about the formation of the giant neutral cloud of water molecules and water products that surrounds Saturn out to a distance of ∼12 planetary radii and about the genesis and evolution of the rings.The INMS instrument consists of a closed ion source and an open ion source, various focusing lenses, an electrostatic quadrupole switching lens, a radio frequency quadrupole mass analyzer, two secondary electron multiplier detectors, and the associated supporting electronics and power supply systems. The INMS will be operated in three different modes: a closed source neutral mode, for the measurement of non-reactive neutrals such as N₂ and CH₄; an open source neutral mode, for reactive neutrals such as atomic nitrogen; and an open source ion mode, for positive ions with energies less than 100 eV. Instrument sensitivity is greatest in the first mode, because the ram pressure of the inflowing gas can be used to enhance the density of the sampled non-reactive neutrals in the closed source antechamber. In this mode, neutral species with concentrations on the order of ≥10⁴ cm⁻³ will be detected (compared with ≥10⁵ cm⁻³ in the open source neutral mode). For ions the detection threshold is on the order of 10⁻² cm⁻³ at Titan relative velocity (6 km sec⁻¹). The INMS instrument has a mass range of 1–99 Daltons and a mass resolutionM/ΔM of 100 at 10% of the mass peak height, which will allow detection of heavier hydrocarbon species and of possible cyclic hydrocarbons such as C₆H₆.The INMS instrument was built by a team of engineers and scientists working at NASA’s Goddard Space Flight Center (Planetary Atmospheres Laboratory) and the University of Michigan (Space Physics Research Laboratory). INMS development and fabrication were directed by Dr. Hasso B. Niemann (Goddard Space Flight Center). The instrument is operated by a Science Team, which is also responsible for data analysis and distribution. The INMS Science Team is led by Dr. J. Hunter Waite, Jr. (University of Michigan).This revised version was published online in July 2005 with a corrected cover date.