圆盘旋转爆震燃烧室中爆震波传播模态

为了研究圆盘结构下旋转爆震波传播特性,通过求解14组分19步CH4/O2反应的欧拉方程,数值模拟了不同燃料喷射温度、压力、燃烧室内外直径比值和燃烧室径向长度并分析了其对旋转爆震波传播模态的影响.研究表明,只有预混气喷射温度为500～900K,喷射压力为0.5～3.5MPa的条件下能够在固定燃烧室内形成连续的旋转爆震波....     

高海况下反舰导弹对舰船目标攻击策略

反舰导弹攻击海面舰船目标时,通常根据目标的散射特征数据进行目标类型判定并做出决策。但是在高海况下:如果导弹横浪飞行,海浪对导弹命中目标的影响会变小,基本能保证可靠命中目标;但如果导弹顶浪飞行,则海浪会引起目标雷达反射截面积(Radar Cross Section,RCS)的起伏甚至突变,影响导弹对目标的锁定和判断。文章建立了不同海况和舰船目标的融合模型,并针对融合模型仿真计算了导弹不同突击方向时的 RCS,最终根据高海况时舰船横浪或顶浪航行的原则,按照捕捉概率最大的方向确定导弹的攻击方向。     

Anomalous particle transport in the heliosphere

The transport of energetic particles in the presence of magnetic turbulence can exhibit a variety of regimes different from the standard quasilinear diffusion. Here we discuss a number of solar and space problems where nonquasilinear diffusion is found, and then we illustrate anomalous transport regimes, for which the mean square deviation grows nonlinearly with time. In particular, we concentrate on superdiffusive regimes, and show what is the theoretical framework which is to be used to describe superdiffusion. We discuss the results of numerical simulations which show that superdiffusive and subdiffusive regimes are possible, and describe data analyses which allow to single out the superdiffusive transport from the observation of energetic particle profiles upstream of interplanetary shocks. The implications of superdiffusion on the efficiency of wave particle interactions are also discussed.     

DEMETER卫星记录到的电离层加热现象

在法国DEMETER卫星运行期间, 地基电离层加热装置SURA和HAARP开展了一系列加热试验, 记录到各类电离层异常信息, 发现电离层加热过程中卫星观测的电离层扰动信号包括HF发射泵波及边带泵波、VLF人工源增强及频谱拓展、ULF/ELF/VLF调制波、ELF电磁扰动、ULF谐振波、等离子体特征参量扰动及高能粒子沉降等. 由于传播及耦合机制的差异, 发射泵波可以穿透电离层直达卫星高度, 其观测概率最高达到68%以上, 其他扰动受发射调制模式及当地电磁环境等影响,观测概率相对较低, 均在40%左右, 有些甚至是某次试验中出现的个别事例. 结合中国地震电磁监测试验卫星飞行轨道设计及载荷配置等,对未来开展加热试验进行了分析论证, 并参考DEMETER卫星试验结果给出了一些建议.     

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.     

Broadband electrostatic noise and low-frequency waves in the Earth’s magnetosphere

Broadband electrostatic noise (BEN) is commonly observed in different regions of the Earth’s magnetosphere, eg., auroral region, plasma sheet boundary layer, etc. The frequency of these BENs lies in the range from lower hybrid to the local electron plasma frequency and sometimes even higher. Spacecraft observations suggest that the high and low-frequency parts of BEN appear to be two different wave modes. There is a well established theory for the high-frequency part which can be explained by electrostatic solitary waves, however, low-frequency part is yet to be fully understood. The linear theory of low-frequency waves is developed in a four-component magnetized plasma consisting of three types of electrons, namely cold background electron, warm electrons, warm electron beam and ions. The electrostatic dispersion relation is solved, both analytically and numerically. For the parameters relevant to the auroral region, our analysis predict excitation of electron acoustic waves in the frequency range of 17 Hz to 2.6 kHz with transverse wavelengths in range of (1–70) km. The results from this model may be applied to explain some features of the low-frequency part of the broadband electrostatic noise observed in other regions of the magnetosphere.     

燃烧室宽度对煤油旋转爆震波传播模态的影响—“爆震专刊”

为研究基于煤油的旋转爆震波的传播特性,以煤油和含氧量40%的富氧空气作为燃料和氧化剂,基于燃烧室外径均为100 mm的无内柱燃烧室和燃烧室宽度分别为32 mm、26 mm和20 mm的环形燃烧室开展了对比实验。不同氧化剂流量下,共观察到四种燃烧波模态,分别为爆燃模态、准稳定爆震模态、双波对撞模态和稳定旋转爆震模态。无内柱燃烧室中,氧化剂流量较低时无法维持旋转爆震波的稳定传播,出现爆燃模态和准稳定爆震模态;当氧化剂流量超过120 g/s时,可以得到旋转爆震模态,旋转爆震波峰值压力超过0.7 MPa,平均传播速度为1750 m/s。对于环形燃烧室,旋转爆震波的传播速度仅为1245~1465 m/s,明显低于无内柱燃烧室中的传播速度。随环形燃烧室宽度减小,对应旋转爆震波模态的工况范围更窄,传播速度更慢。在本研究对应的工况范围内,增大燃烧室宽度,更有利于基于煤油的旋转爆震波的稳定传播。     

子午面内Alfvén波的传播特征

本文使用由ＷＫＢ近似得到的Ａｌｆｖｅｎ波传播的张量表达式,具体计算和讨论了一种太阳子午面内含盔形－电流片磁位形的流场中Ａｌｆｖｅｎ波的传播特征,主要结果是：（１）Ａｌｆｖｅｎ波磁场起伏随日心距离的增加而衰减,其中极开区的衰减远快于赤道区,但随着距离的增大,这种纬度关系将迅速变弱,以致在较远空间,磁起伏相差很小,衰减很慢;（２）Ａｌｆｖｅｎ波的相对磁场起伏ｂ／Ｂ随着距离的增加而迅速增大,在几个太阳半径之后变化不再明显,达到所谓的＂饱和＂;在大日心距离的盔形电流片附近,Ａｌｆｖｅｎ波将成为重要的磁场组成部分;（３）Ａｌｆｖｅｎ波速度起伏纬度关系较为明显,相对速度起伏。ｕ／Ｕ随着距离增大而衰减,电流片区衰减得较快,但这种纬度差别将变弱．与黄道面内Ａｌｆｖｅｎ波传播特征的具体比较表明,磁场涨落的变化特征与背景场位形存在着十分密切的关系,但速度涨落与背景场没有这种明显关系．     

太阳风里高能电子自发辐射的Langmuir波

本文讨论太阳风里太阳耀班高能电子产生的Langmuir波的自发辐射。理论估计得出,在时间尺度γ_km-1内,Langmuir波自发辐射的电场幅值约为10-3-10-2mV/m(依赖于高能电子速度分布的具体形式),这里γ_km为在波数k处的峰增长率。此理论结果比飞船在太阳风里的观测值低2-3个数量级。因此认为,太阳风里自发辐射产生的Langmuir波辐射是可以忽略的。      

Study of VLF wave with relativistic effect in Saturn magnetosphere in the presence of parallel A.C. electric field

Cassini radio and plasma wave surveys aim to study radio emissions, plasma waves, thermal plasma and dust near Saturn. Using the characteristic solution and dynamics method, the influence of electron beam on the loss cone and bi-Maxwellian distribution of whistler mode waves in the parallel alternating electric field and magnetic field is studied. The dispersion relation and the growth rate of Saturn's magnetic layer were deduced and calculated in detail. Parameter analysis is performed by changing the parameters of the plasma like number density, AC frequency, temperature anisotropy, etc. The influence of AC frequency on Doppler shift and the comparative study of growth rate of oblique and parallel propagating waves are analyzed using generalized distribution function. We found temperature anisotropy ${\text{A}}_{\text{T}}=1.25$ can explain the linear spatiotemporal growth rate of whistler mode waves. It provides the majority of the observed frequency integral power. It can be seen that the effective parameters for the generation of Whistler mode waves are not only temperature anisotropy, but also the relativistic factors discussed in the results and discussion section, and the AC field frequency and width of the loss cone distribution function.