修正的跨声速小扰动方程以及与其相容的激波方程

本文给出了与修正的跨声速小扰动(MSD)方程相容的激波方程,计算证明它的极曲线与精确的激波极曲线十分接近。     

温度、密度对目标等离子体隐身效果影响的FDTD分析

采用等温近似,给出覆盖目标的不均匀的、各项同性的、热的、碰撞的、等离子体的电磁反射的三维FDTD算法的公式。在一维条件下,计算了不同密度分布、不同温度的等离子体对电磁波的反射系数。给出了温度、密度对电磁波在等离子体中的碰撞吸收的影响。结果显示,增大等离子体的温度和密度将有利于等离子体对电磁波的吸收,增大吸收的带宽,减小等离子体覆盖目标对电磁波的反射。     

TYPES OF FLOW OVER LEESIDE OF A SLENDER TAPERED WING AT SUPERSONIC SPEED

ＴＹＰＥＳＯＦＦＬＯＷＯＶＥＲＬＥＥＳＩＤＥＯＦＡＳＬＥＮＤＥＲＴＡＰＥＲＥＤＷＩＮＧＡＴＳＵＰＥＲＳＯＮＩＣＳＰＥＥＤＨｏｎｇＪｉｎｓｅｎ（ＢｅｉｊｉｎｇＩｎｓｔｉｔｕｌｅｏｆＡｅｒｏｎａｕｌｉｃｓ，Ｂｅｉｊｉｎｇ，Ｃｈｉｎａ，１０００７４）Ａｂｓ...     

太阳色球层-日冕中扰动的传播(Ⅱ)

首先讨论了磁流波传播的线性特征，然后构造了球坐标中-自治的非等温，非均匀等离子体初态，应用二维时变可压缩磁流体动力学模拟，数值研究了色球层底部压力脉冲所引起扰动的全球传播过程，结果表明，在极区，压力脉冲导致的扰动传播可以区分成两类不同模式的波动，快磁声波与慢磁声波，而在赤道附近，传播扰动是快模磁声波，在源区附近还存在一非传播的扰动，模拟结果的特征有助于解释SOHO/EIT观测到的波动事件。     

Binary and millisecond radio pulsars

Recent pulsar surveys, especially those using the multibeam receiver on the Parkes radio telescope, have more than doubled the number of known pulsars, bringing the current total to about 1720. Of these, 171 have millisecond periods, 126 are members of binary systems and 99 are associated with globular clusters. Binary pulsars may be divided into several distinct groups depending on their observed properties such as pulsar period and age, binary period, eccentricity and companion mass. These groups all have different evolutionary histories. Correlations between the various properties are discussed using the increased samples now available. The Parkes Pulsar Timing Array is a project which has the goal of using timing observations of millisecond pulsars to make a direct detection of gravitational waves. The parameters and present status of the project are briefly discussed.     

Self-consistent amplitude profile of ducted VLF transmitter signal due to resonant interaction with energetic electrons in the magnetosphere

Of the various sources of whistler waves in the magnetosphere, the signals from terrestrial VLF transmitters are apparently the simplest for theoretical analysis. The role of these signals in the acceleration and pitch-angle scattering of energetic electrons in the Earth’s radiation belts has not been fully studied quantitatively, despite many decades of relevant research. The main problem in studying this issue is that to calculate the acceleration and pitch-angle scattering of particles, it is necessary to know the spatial profile of the signal amplitude. This is especially critical for phase-trapped particles, for which the energy exchange with the wave is the most significant. At the same time, the wave amplitude profile itself is determined by the interaction of the wave with resonant particles. Thus, we are dealing with a self-consistent problem, which is described by a nonlinear system of equations - a kinetic equation for the distribution function of resonant particles with a self-consistent field, and an equation for the wave field, in which the nonlinear and non-local growth rate is determined by the distribution function of resonant particles. In this paper, we develop an approach to solving this system of equations and the corresponding physical problem using the method of successive approximations.     

Absolute and Convective Instabilities of Circularly Polarized Alfvén Waves

We discuss the recent progress in studying the absolute and convective instabilities of circularly polarized Alfvén waves (pump waves) propagating along an ambient magnetic field in the approximation of ideal magnetohydrodynamics (MHD). We present analytical results obtained for pump waves with small dimensionless amplitude a, and compare them with numerical results valid for arbitrary a. The type of instability, absolute or convective, depends on the velocity U of the reference frame where the pump wave is observed with respect to the rest plasma. One of the main results of our analysis is that the instability is absolute when U _l < U < U _r and convective otherwise. We study the dependences of U _l and U _r on a and the ratio of the sound speed to the Alfvén speed b. We also present the results of calculation of the increment of the absolute instability on U for different values of a and b. When the instability is convective (U < U _l or U > U _r) we consider the signalling problem, and show that spatially amplifying waves exist only when the signalling frequency is in two symmetric frequency bands. Then, we write down the analytical expressions determining the boundaries of these frequency bands and discuss how they agree with numerically calculated values. We also present the dependences of the maximum spatial amplification rate on U calculated both analytically and numerically. The implication of the obtained results on the interpretation of observational data from space missions is discussed. In particular, it is shown that circularly polarized Alfvén waves propagating in the solar wind are convectively unstable in a reference frame of any realistic spacecraft.     

基于综合平面波技术的近远场变换

近场散射数据的远场变换研究是具有发展前景的由近场测量目标,获取目标远场雷达截面的方法之一。根据近场获得的散射数据,外推获取远场的目标散射特性。主要是利用平面波谱展开,推导了近远场转换公式;以导体圆柱、平板等简单物体作为散射体仿真了近场散射数据的远场变换,证明了方法的可行性和正确性。     

振动温度的激波管测定

根据双原子分光带系及其强度理论,介绍了测定振动温度的原理及方法。同时,利用激波加热试验气体的方法,得到氧化铝分子绿带系(B~2∑~+-X~2∑~+)的全部光带。通过氧化铝分子绿带系光带强度的测定,得到在激波马赫数为10时,反射激波后气体的振动温度约为5200K。