Study of the solar Slow Sonic,Alfvén and Fast Magnetosonic transition surfaces

In this paper we study the shape, extend and time variations of the solar wind transition surfaces using the Lima and Priest (1993) hydrodynamic model adequately adapted for the case of the solar wind flow. The transition surfaces, namely the Slow (Sonic), the Alfvén, and the Fast Magnetosonic surface, are important boundaries around the Sun and play a crucial role in the development of the solar wind and the structure of the inner heliosphere. We determine the shape and dimension of these surfaces as a function of heliographic latitude using measurements from Ulysses spacecraft, and we also study their temporal variation using data from spacecrafts at 1 AU (OMNI database). Furthermore, we establish their dependence with the solar activity, demonstrating their shape and location for the last two solar cycles. From this we noticed that the temporal variation of all transition surfaces follows the 11-year solar cycle. Finally, from the OMNI database, we have studied the temporal variation over the past 40 years of the plasma β parameter, the kinetic to magnetic and the kinetic to thermal energy ratios, at a distance of 1 AU from the Sun.     

低温红外镜头星点检测数据处理方法研究

在实验室模拟低温真空环境对红外镜头进行星点检测时,不能在像面处直接测得星点光源的像,而是通过在焦面处放置反射镜使系统二次成像的方法测得二次成像的弥散斑大小。二次像斑尺寸的变化将能反映出由温度变化引起的被测镜头焦面处像斑尺寸的变化。通过理论推导得出一次像与二次像弥散斑大小的数学关系,并通过对不同尺寸星点光源、不同像质光学系统的仿真分析,得出星点检测法的检测精度与星点孔直径有关,而与镜头本身成像品质无关。     

来流扰动对圆盘绕流结构影响的实验研究

主要讨论由水槽流动显示实验得到的圆盘绕流结构在上游小圆柱尾迹干扰下的变化,对圆盘前驻点附近逆压区的流动通过氢气泡显示技术进行观察.由实验结果处理得到圆盘前大涡的结构特征(如周期、最大宽度、在周期内结构随时间的变化等)受扰动几何参数的影响.发现无量纲参数L/d(L为小圆柱中心与圆盘迎风面之间的间距,d为小圆柱直径)对圆盘前驻点区域中大涡的形成和发展有重要的影响.圆柱尾迹中涡通量的增加会在圆盘前产生大尺度的涡对,其周期性演化的频率随L/d增加而增加.     

基于视线矢量的深空自主导航算法研究

针对深空探测器在行星际飞行的轨道确定问题, 研究了一种基于视线矢量的自主导航算法. 结合深空探测任务的特点, 以太阳视线矢量和地球视线矢量作为导航系统的观测量, 在详细分析太阳敏感器测量原理的基础上, 给出了太阳视线矢量的观测模型及其观测误差表达式. 通过分析导航相机观测原理, 给出像元像线观测模型, 并推导了地球视线矢量的观测误差. 根据惯性空间内视线矢量间的几何关系, 详细推导了探测器的位置矢量及其误差表达式, 结合非线性扩展卡尔曼滤波建立自主导航算法. 利用深度撞击任务的实际飞行数据对本文提出的深空自主导航算法进行了仿真验证.     

空间环境中S781和SR107性能退化研究

文章主要研究S781和SR107两种白漆样品在紫外/质子/电子综合辐照环境下太阳吸收率αs的退化情况,利用x射线光电子能谱（XPS）和扫描电子显微镜（SEM）对比两种样品的表面成分和形貌变化,并利用数学模型对S781和SR107的长期退化情况进行了预示。结果表明：SR107白漆的表面完全被甲基硅橡胶粘合剂包覆,辐照前后成分变化不大;S781白漆在辐照后表面出现裂痕,成分也有所改变。在辐照开始后SR107的太阳吸收率αs比S781更快趋于稳定,但退化得更严重。     

太阳光谱线轮廓在日面上的变化和宁静太阳大气模型

本文利用在美国基特峰国家天文台观测得到的氢和电离钙多条谱线轮廓,以及PANDORA大气模型计算程序,对宁静太阳VAL-C'大气模型进行了诊断。文中首先讨论了模型大气中不同层次的辐射特性,着重指出H巴尔末谱线同Call共振线和红外线的源函数具有与温度不同的耦合关系。其次,通过计算得到了各条谱线在日面不同点的出射轮廓,并将其同观测轮廓相比较,存在的系统差别有:(1)Hβ和λ8498红外线线心的剩余强度较观测值高,而CaIIH和K线线翼的剩余强度则明显比观测值低;(2)Hβ及caII各条谱线在△λ=0.5Å处的剩余强度值的临边增大系数较观测值大。除上所述及某些观测误差以外,计算值同观测值符合得较好。最后,文章分析了导致计算和观测不符的可能原因,并进而提出了对VAL-C'模型改进的意见。     

The determination for ideal release point of test masses in drag-free satellites for the detection of gravitational waves

Gravitational waves are ripples in space–time predicted by Albert Einstein's general relativity and provide a new way to understand the universe. Space-borne detectors of gravitational waves, extending to very large scales, can effectively detect the middle and low-frequency gravitational wave source with the frequency band of 0.1 mHz–1 Hz. The test masses are used to make an inertial reference point in the detection of gravitational waves. Currently, there are few studies concerning the ideal release position for the test masses in the detection of gravitational waves. In this study, we give a general solution for test mass release points to minimize the relative motion between the test mass and the satellite mass center. Moreover, we discuss the situation when the release point equation is not satisfied, and the ideal release point of the along-track. Finally, we report on simulations that verify the accuracy of the theoretical derivation.     

Magnetic connectivity and solar energetic proton event intensity profiles at deka-MeV energy

We present an analysis of the time-intensity profiles of 25 solar energetic proton events at 18.2 MeV, modelled by fitting an analytical function form (a modified Weibull function) to the observed intensities. Additionally relying on previous work that characterized the magnetic connectivity between the event-related solar flare and the observer in these events with three angular parameters, we investigate the fit function parameters, the connectivity parameters, and the iron-to-carbon ratio of the events for dependencies and correlations. We find that the fit parameter controlling the basic shape of the profile (parameter a) is not clearly dependent on the connectivity parameters or the Fe/C ratio, suggesting that the profile shapes of neither well and weakly connected nor generally “impulsive” and “gradual” events differ systematically during the early stages of the event at 1 AU. In contrast, the time scaling of the fit function (parameter b) is at least moderately correlated with both the magnetic connectivity parameters and the Fe/C ratio, in that well-connected and iron-rich events are typically shorter in relative duration than weakly connected and nominal-abundance events; intensity rise times display a similar correlation with the connectivity parameters. We interpret the former result as following from the combined effect of various transport processes acting on the particles in interplanetary space, while the latter is essentially consistent with established knowledge regarding the observed dependence of the time-intensity profile shapes of solar energetic particle events on their magnetic connectivity and heavy ion abundances. The desirability of modelling the particle transport effects in detail and extending the analysis to cover higher energies is indicated.     

Metrology on-board PROBA-3: The shadow position sensors subsystem

PROBA-3 is an ESA mission aimed at the demonstration of formation flying performance of two satellites that will form a giant coronagraph in space. The first spacecraft will host a telescope imaging the solar corona in visible light, while the second, the external occulter, will produce an artificial eclipse. This instrument is named ASPIICS (Association of Spacecraft for Polarimetric and Imaging Investigation of the Corona of the Sun). To accomplish the payload's scientific tasks, PROBA-3 will ensure sub-millimeter reciprocal positioning of its two satellites using closed-loop on-board metrology. Several metrology systems will be used and the Shadow Position Sensor (SPS) subsystem senses the penumbra around the instrument aperture and returns the 3-D displacement of the coronagraph satellite, with respect to its nominal position, by running a dedicated algorithm. In this paper, we describe how the SPS works and the choices made to accomplish the mission objectives.     

Solar physics with the Square Kilometre Array

The Square Kilometre Array (SKA) will be the largest radio telescope ever built, aiming to provide collecting area larger than 1?km². The SKA will have two independent instruments, SKA-LOW comprising of dipoles organized as aperture arrays in Australia and SKA-MID comprising of dishes in South Africa. Currently the phase-1 of SKA, referred to as SKA1, is in its late design stage and construction is expected to start in 2020. Both SKA1-LOW (frequency range of 50–350?MHz) and SKA1-MID Bands 1, 2, and 5 (frequency ranges of 350–1050, 950–1760, and 4600–15,300?MHz, respectively) are important for solar observations. In this paper we present SKA’s unique capabilities in terms of spatial, spectral, and temporal resolution, as well as sensitivity and show that they have the potential to provide major new insights in solar physics topics of capital importance including (i) the structure and evolution of the solar corona, (ii) coronal heating, (iii) solar flare dynamics including particle acceleration and transport, (iv) the dynamics and structure of coronal mass ejections, and (v) the solar aspects of space weather. Observations of the Sun jointly with the new generation of ground-based and space-borne instruments promise unprecedented discoveries.