Simulation study of motion of charged particles trapped in Earth’s magnetosphere

This article aims to understand the motion of the charged particles trapped in the Earth’s inner magnetosphere. The emphasis is on identifying the numerical scheme, which is appropriate to characterize the trajectories of the charged particles of different energies that enter the Earth’s magnetosphere and get trap along the magnetic field lines. These particles perform three different periodic motions, namely: gyration, bounce, and azimuthal drift. However, often, the gyration of the particle is ignored, and only the guiding center of the particle is traced to reduce the computational time. It is because the simulation of all three motions (gyro, bounce, and drift) together needed a robust numerical scheme, which has less numerical dissipation. We have developed a three-dimensional test particle simulation model in which the relativistic equation of motion is solved numerically using the fourth and sixth-order Runge-Kutta methods. The stability of the simulation model is verified by checking the conservation of total kinetic energy and adiabatic invariants linked with each type of motion. We found that the sixth-order Runge-Kutta method is suitable to trace the complete trajectories of both proton and electron of a wide energy range, 5 keV to 250 MeV for L = 2 – 6. We have estimated the bounce and drift periods from the simulations, and they are found to be in good agreement with the theory. The study implies that a simulation model with sixth-order Runge-Kutta method can be applied to the time-vary, non-analytical form of magnetic configuration in future studies to understand the dynamics of charged particles trapped in Earth’s magnetosphere.     

浅谈企业内部控制制度

内部控制是衡量现代企业管理的重要标志,本文结合目前企业的管理经验,对建立企业内部控制制度的意义、作用、内容、基本原则、应注意的问题进行了论述。     

焊缝补强方式对大直径贮箱箱底承载性能影响

基于有限元法研究了典型10 m级直径贮箱箱底焊缝在双面对称补强、内表面补强及外表面补强三种情况下的内压承载性能。数值计算采用二维对称平面模型,考虑了筒段和短壳真实边界条件及焊缝对承载能力的影响,构建的考虑材料塑性的非线性数值分析模型准确地获得了贮箱箱底内外表面经向应力。结果表明:顶盖和瓜瓣焊缝区域是箱底的薄弱位置,使用内压下,双面对称补强的加强区内外表面经向应力差较小,结构均未进入塑性,单面补强的加强区内外表面经向应力差远大于双面对称补强,局部进入塑性,且外表面补强的加强区最大和最小经向应力差相对于内表面补强分别增加了9.7%和27.2%,变形不协调；设计内压下,箱底内外表面均有局部进入塑性,材料塑性对内外表面经向应力差有一定的缓解作用,能够显著缓解内外表面应力差造成的附加弯矩；双面对称补强优于内表面补强,内表面补强优于外表面补强,单面补强易产生附加弯矩,不利于箱底的均匀承载和变形协调。该研究结果指导了大直径贮箱箱底结构的优化设计。     

MHD surface waves – a source of global magnetospheric modes (resonances)?

Various mechanisms have been proposed for explanation of the global magnetospheric modes whose frequency peaks are in the frequency range 1–4 mHz. Recent papers claim: basic characteristics of the 1–4 mHz activity events observed on ground give evidences for an existence of MHD surface mode excited on the Earth magnetopause. The discrete frequencies of such MHD surface wave modes suggest an emergence of standing wave structures along the magnetic field lines lying on the magnetopause. Such discrete frequencies of MHD surface waves on magnetopause however, are not stable, at all. Contrariwise, MHD surface wave modes supported by the two plasma boundaries – the magnetopause and the plasmapause, are in accordance with existing experimental facts: discrete set of almost stable frequencies, field amplitude peaks and positions, energy dissipation, and field distribution from high to low latitudes. Mechanisms of the global magnetospheric mode resonance are pointed out as well as tools for their identification and discrimination.     

Some peculiarities of longitudinal distribution of proton fluxes at high latitudes

Dynamical features of proton fluxes at high and middle latitudes were studied based on data measured by Sun-synchronous low-altitude (800 km height) polar-orbiting three NOAA series satellites: POES 15, 16, and 17 during the geomagnetic storm on January, 21–22, 2005. Data from three satellites that passed the Northern hemisphere along different MLTs allow reconstructing the longitudinal distribution of the proton fluxes. Measurements of protons with energies of 30–80 keV and 80–240 keV (the ring current energy range) by 0- and 90-detectors were used to evaluate and compare the longitudinal asymmetry of proton flux distribution measured in the regions equatorward and poleward of the isotropic boundary. It was found that during all the phases of the geomagnetic storm distribution of the maximum flux of precipitating protons (0-detector data) is sufficiently asymmetric. The maximal flux position along MLT is moving from pre-midnight sector in quiet time to post-midnight one before and during SSC and moving back during recovery phase. The longitudinal distribution of precipitation maxima demonstrates the local increase in afternoon sector (approximately at 13:30 MLT) and decrease in the dusk one during SSC. These features are evident consequence of the magnetosphere compression. To identify the origin of the particles, the locations of maximum fluxes have been projected to the magnetosphere. It was determined that during geomagnetic storm main and recovery phases maximum fluxes were measured at latitudes poleward of the isotropic boundary. To evaluate the trapped particle flux asymmetry, the particle fluences (90-detector data) were calculated along the satellite orbit from L = 2 to the isotropic boundary. The total fluences of trapped particles calculated along the satellite orbit show regular asymmetry between dusk and dawn during main and recovery phases. The maximal intensity of proton fluxes of both investigated populations located poleward and equatorward of the isotropic boundary is achieved during SSC. The total flux measured during crossing the anisotropic region can be considered as a proxy for ring current injection rate.     

用内文丘里管流量计测量酸气流量

介绍了新型差压装置--内文丘里管的结构、测量原理、技术性能;根据差压式流量计的测量原理,建立了计算酸气流量的数学模型,并将内文丘里管流量计成功地应用于酸气流量的测量.     

One-up on L1: Can X-rays provide longer advanced warning of solar wind flux enhancements than upstream monitors?

Observations of strong solar wind proton flux correlations with ROSAT X-ray rates along with high spectral resolution Chandra observations of X-rays from the dark Moon show that soft X-ray emission mirrors the behavior of the solar wind. In this paper, based on an analysis of an X-ray event observed by XMM-Newton resulting from charge exchange of high charge state solar wind ions and contemporaneous neutral solar wind data, we argue that X-ray observations may be able to provide reliable advance warning, perhaps by as much as half a day, of dramatic increases in solar wind flux at Earth. Like neutral atom imaging, this provides the capability to monitor the solar wind remotely rather than in situ.     

中介轴承环下流道滑油流动及润滑效率分析

航空发动机主轴轴承（中介轴承）大多采用环下供油方式进行润滑,滑油在环下供油流道中的流动特性影响着轴承润滑效率,为了改善迄今滑油流动分析与喷射-收纳滑油分析相割裂及未考虑环下供油孔与滚动体相对位置变化所产生滑油输出时变性影响的不足,提出了考虑滑油输出时变性影响的喷油-收油与滑油流动集成分析方法。首先,将进入环下供油流道的滑油分解为直接喷入收油孔的滑油和沉积于收油环壁面上并沿周向流入收油孔的滑油,通过计算这两部分滑油流量获得进入环下供油流道的滑油流量;然后,基于环下供油孔和滚动体相对位置变化规律确定供油孔出口的时变边界条件,将其嵌入滑油流动瞬态分析模型,进行模型求解后得到环下供油流道各出口的滑油流量及轴承润滑效率。所提出的滑油流动分析方法较为系统也更符合工程实际,为中介轴承润滑效率的准确计算提供了技术方法和基础数据,有助于中介轴承润滑系统的精确设计。     

ARINC659总线在IMA架构中的适用性分析

综合模块化航电系统在飞机航电设备的研制中逐渐得到应用,实现综合化模块化航电的一个关键技术是系统内部总线的选择,通过论述综合模块化航电系统对系统内部总线的要求、介绍ARINC659总线的特点,分析ARINC659总线在综合模块化航电系统中的适用性,可以得出ARINC659总线能够满足综合模块化航电系统的要求,目前ARINC659总线已经开始广泛应用于综合模块化航电系统中.     

GH3600精细薄壁管内壁折叠缺陷分析

为了提高GH3600精细薄壁管质量,利用内窥镜和扫描电镜,对管材内壁折叠缺陷进行了解剖观察,测量了折叠的深度,并分析了折叠缺陷产生的原因和它对后续成型的影响,提出了避免折叠缺陷的工艺改进措施。