An investigation of high frequency auroral plasma emissions with a tubular dipole antenna

A band of enhanced amplitudes which follows a local plasma frequency fn in raw high frequency (HF) noise spectra is usually related to plasma emissions in the upper hybrid band (fn, fu). The enhanced band in question occurs permanently in noise spectra recorded on the Intercosmos-19, APEX and CORONAS satellites in the altitude range of 500 km–3000 km. For moderately magnetized plasma with fn > 2fc (fc – electron gyro frequency), the band occurs below fn determined from the topside sounder and impedance data or from electron beam induced spectra. The simulations of an equivalent circuit composed of a dipole antenna in a cold plasma and its preamplifiers, determined the physical origin of the band as the passive circuit resonance, due to inductive character of the antenna in a frequency band (fc, fu). The resonance spectral content is highly structured due to an inflight variability of the circuit impedances. In this report we analyze the noise and impedance spectra which are the most typical in an auroral zone if fn > fc. We focus attention on determination of local electron plasma density, essential for provisional HF mode classification. We found that the natural plasma emission in the upper hybrid band does not manifest itself as the banded natural emission, which may be used for reliable determination of local plasma frequency in the altitude range of 500–3000 km. The fast magnetosonic mode predominates in the auroral emissions. The broadband and multi banded electromagnetic emissions extending from the fast magnetosonic band well above fn > fc are characteristic for the strong wave activity and are much less frequent.     

Testing the no-hair theorem with observations of black holes in the electromagnetic spectrum

According to the no-hair theorem, astrophysical black holes are uniquely described by their mass and spin. In this paper, we review a new framework for testing the no-hair hypothesis with observations in the electromagnetic spectrum. The approach is formulated in terms of a Kerr-like spacetime containing a quadrupole moment that is independent of both mass and spin. If the no-hair theorem is correct, then any deviation from the Kerr metric quadrupole has to be zero. We show how upcoming VLBI imaging observations of Sgr A∗ as well as spectroscopic observations of iron lines from accreting black holes with IXO may lead to the first astrophysical test of the no-hair theorem.     

微孔推进剂稳定燃烧条件的初步计算研究

建立了一个描述微孔推进剂燃烧的模型，并得到了推进剂稳定燃烧时的控制方程组。计算了燃烧室压力与初始空隙率等对燃烧过程的影响，分析了稳定燃烧时应满足的一些基本条件，结果与实验值相一致。     

二维非结构网格DSMC方法的实现及其应用

研究了非结构网格DSMC方法实现的过程，将Bird位置元方案中的子网格思想引入到非结构网格上来，只存储子网格的总体标识号，做到了利用较少的计算网格提高分子的分辨率和计算精度；提出了将面积元坐标搜索算法与交替数字二叉树搜索算法(ADT)相结合来跟踪模拟分子在网格之间的迁移；使用ADT方法判别分子与物面是否相交，节约了计算时间；最后对过渡流域高超声速绕流进行了数值试验．结果表明这种方法的可行性、高效性及算法的通用性。     

基于失效物理的动量轮贝叶斯可靠性评估

作为卫星姿态控制系统关键部件的动量轮,其可靠性关系到卫星发射的成败。但是由于有小子样、高可靠性和长寿命等特点,受技术、费用和时间等条件的限制,无法获得大样本失效寿命数据,因此利用传统的大样本寿命数据统计推断方法进行可靠性建模、分析与评估存在困难。为此,从失效物理分析的角度出发建立性能退化模型,用贝叶斯方法融合性能退化模型和寿命模型得到产品的可靠性评估模型,并基于该模型充分利用失效物理试验中的性能数据和少量的寿命数据来进行可靠性评估。实例分析表明,该方法与伪寿命方法相比更加符合工程实际,评估精度更高。     

空间物理学最新进展与展望

空间物理学是人类进入空间时代后迅速发展的一门新兴交叉学科,特别是进入新世纪后国内外都取得了辉煌的成就.本文简要介绍空间物理领域近年来取得的重要进展、重要成果、国内外发展趋势,以及未来发展的重点方向.     

太阳空间探测进展与展望

摘要：为了探索太阳空间探测活动的发展方向,在广泛调研太阳空间探测任务的基础上,综合考虑任务实施年代、轨道设计、探测要素、技术特点和成果影响力,选取了10个典型空间太阳探测器,对其科学目标、有效载荷、卫星平台特性和科学发现进行了分析,提炼总结了太阳空间探测的进展和发展趋势。总体而言,太阳探测器运行轨道逐步多样化,有效载荷探测要素更加丰富,探测精度、时空分辨率等显著提升,但仍存在大量问题待解决。在分析现阶段成果和待解决问题的基础上,提出了太阳空间探测的发展展望,指出了全方位、多要素探测是破解太阳物理和空间天气预报发展瓶颈的可行途径。     

航天电连接器的振动可靠性建模

通过分析电连接器在振动应力作用下的失效机理，得出了电连接器接触寿命与振动应力之间的影响关系，建立了电连接器在振动应力作用下的失效物理方程，并进行了以随机振动应力为加速因子的恒定应力加速寿命试验，经对试验数据进行统计分析，验证了所建模型的正确性。     

应用空间原子钟的基础物理测试

随着新型原子钟的发明,其频率稳定度性能已经发展到很高的水平,它们在空间科学试验中将发挥重要作用。这篇文章将介绍应用空间原子钟在微重力环境下所建议的某些基础物理方面的测试。     

绕地轨道运动地面物理试验的建模与分析

基于对地面物理试验系统的受力分析建立了数学模型,定性定量地分析了液体阻力、模拟万有引力及推力对运动轨迹的影响.首先,根据椭圆轨道摄动方程组导出了推力、液体阻力、模拟万有引力同时存在时地面物理试验的数学模型;然后,通过理论分析定性定量地给出了推力偏差和模拟万有引力偏差对轨道的影响程度;最后,通过大量的数值模拟验证了理论分析的结果.