低纬Pc3地磁脉动的多台观测

利用长春、北京、兰州三个低纬地区台站的地磁脉动观测资料,对低纬地区(1.21≤L≤1.43)Pc3脉动的频谱特性和偏振特性做了对比分析,并对低纬Pc3脉动的激发机制和传播过程进行了讨论。      

SABRE雷达及其观测的Pc5地磁脉动Ⅰ.统计分析结果

本文简要介绍了相干散射雷达SABRE及其观测Pc5地磁脉动的工作原理。1985—1989年观测数据的统计分析结果表明,相位向极传播脉动事件的出现率峰值在当地时间午夜附近,而向赤道传播事件的出现率峰值则在18:00LT左右。文中给出了上述两类脉动事件出现率的日变化,与地磁活动的相关,与背景电离层等离子体对流特性的关系等统计分析结果。     

中低纬度Pc3-4地磁脉动特性研究——子午工程数据分析初步结果

利用新建成的子午工程地磁台站数据,对比分析了地磁平静期间(2011年3月20-27日)和磁暴期间(2011年9月25日至10月1日)Pc3-4地磁脉动的时空分布特征及其对行星际条件的响应.数据分析结果表明,中低纬度(1.3<L<2.3,L为磁壳参数)的Pc3-4地磁脉动在这两个时期内的分布存在明显的晨昏不对称性,在昼侧前出现明显的Pc3-4地磁脉动并与行星际上游波动密切相关,其振幅增强可能与太阳风动压脉冲相关,高速太阳风更易导致Pc3-4地磁脉动;而对于近赤道低纬(L<1.3)区域,无论是在地磁平静期还是磁暴期均未能观测到Pc3-4地磁脉动,Pc3-4地磁脉动存在明显的纬度效应.      

磁尾爆发性整体流和地磁Pi2脉动关系研究

利用Cluster,TC-1以及中国和欧洲在中低纬六个地面台站的数据,分析了2004年10月22日1700-1930 UT发生的三次BBF事件过程中地面和近地空间磁场脉动的特性.这三次BBF事件都发生在地磁活动的平静时期.结果发现,有两次平静时期的BBF确实对应着阻尼型Pi2脉动,并且脉动的特征与以前观测结果中的特征类似.在第一次BBF事件中,空间观测和地面观测均发现了Pi2脉动;在第二次事件中,地面观测到了Pi2脉动,而空间没有观测到Pi2脉动;在第三次事件中,空间和地面观测都没有发现Pi2脉动.这些观测事实说明BBF所激发的Pi2脉动特征是相当复杂的,而且并不是所有BBF都能产生Pi2脉动,所以到底BBF在什么条件下可以产生Pi2仍然是一个没有解决的问题.      

磁层顶的Kelvin-Helmholtz不稳定性(Ⅳ)可压缩不稳定波的若干特性

本文讨论了磁层顶可压缩K-H不稳定波的若干特性,包括磁场扰动和密度扰动的位相关系,扰动磁场的偏振特性,时间增长率的午前午后非对称性,空间增长率及磁层脉动的地方时效应和K-H不稳定波对IMF的响应。分析表明,上述诸特性对于了解磁层边界区MHD波的起源和K-H不稳定性同地磁脉动的关系十分重要。      

1998年5月空间天气大事件的地磁场响应

地磁场与1998年5月空间大事件相对应的是5月1日至16日发生的大磁暴（k=8)。磁暴主相开始的几个小时伴随有丰富的Pc型地磁脉动，包括P c2,Pc3,Pc4等。在增暴的恢复相，甚至还有Pc5巨型脉动，在行星标磁场Bz由北向转向南向时，磁暴主相开始；南向分量达到最大值后大约2小时，地磁H分量达到最小值，恢复相开始，并且，这次磁暴与太阳风电场也存在一定的对应关系。     

太阳风中动力论Alfven波的湍流普（a）朗道衰减

提出了一个太阳风中Ａｌｆｖｅｎ脉动湍流的新模式，动力论Ａｌｆｖｅｎ波和离子声波非解耦的新波模同，由太阳向外传播的各种波长的动力Ａｌｆｖｅｎ波的非线性相互作用推导出动力论Ａｌｆｖｅｎ脉动湍流功率谱Ｐｋ，在Ａｌｆｖｅｎ半径以外，Ｐｋ∞＾３／２而在Ａｌｆｖｅｎ半径以内，由太阳附近的Ｐｋ∞ｋ＾－１变化成Ｐｋ∞ｋ＾－３／２。     

Alfven波在微电离大气中的衰减特性研究

利用简单的偶极子地磁场模型以及大气电子密度和电导率模式, 分析地面产生的磁扰动以Alfven波的模式传播到近地空间区域. 这种地面的磁扰动可能干扰近地空间卫星对空间磁扰动的观测. 通过对地面磁扰动Alfven波模式1000 km高度内的衰减情况进行模拟, 认为在近地空间采用地磁偶极子模型是合理的. 由于衰减随扰动频率的增大而急剧增强, 分析还得到了近地卫星能够探测到地面磁扰动的最大频率. 计算结果表明, Alfven波的衰减主要集中在高度50 km以下, 这个区域内的大气电导率极其微弱, 使Alfven波的传播受到极大衰减. 0.4 Hz以下的Alfven波沿磁力线传播到1000 km高度后衰减结为原来扰动幅度的千分之一, 因此频率在0.4 Hz以下的Alfven波可能会干扰低轨卫星探测磁场脉动.      

太阳风中动力论Alfven波的湍流谱(a)朗道衰减

提出一个太阳风中Alfven脉动湍流的新模式,动力论Alfven波是Alfven波和离子声波非解耦的新波模。由太阳向外传播的各种波长的动力Alfven波的非线性相互作用推导出动力论Alfven脉动湍流功率谱P_k,在Alfven半径以外,P_k∝k-3/2,而在Alfven半径以内,由太阳附近的P_k∝k-1变化成P_k∝k-3/2动力论Alfven脉动在Alfven半径以内完成朗道衰减。新模式克服了以前理论模式遇到的困难。      

1991年3月太阳活动引起的地磁扰动

利用北京白家疃台和马道峪台的地磁资料分析了1991年3月下旬太阳活动引起的24－27日的磁暴，从中纬记录看，这次磁暴有其特殊的形态：即急始幅度特别大，磁暴最强活动是急始后即刻开始的极区暴影响而产 生的：磁暴过程中多个时段出现脉动，其中以周期为650秒左右的脉动尤为明显；其极化方向主要表现为左旋偏振，同时夹有右旋偏振，有时则无明显规律，谱分析的结果表明，整个磁暴功率谱呈幂律P(f)=f^-2,0分布，对引起这次磁暴可能的行星际扰动进行了讨论。     

Scaling analysis and model estimation of solar corona index

A monthly average solar green coronal index time series for the period from January 1939 to December 2008 collected from NOAA (The National Oceanic and Atmospheric Administration) has been analysed in this paper in perspective of scaling analysis and modelling. Smoothed and de-noising have been done using suitable mother wavelet as a pre-requisite. The Finite Variance Scaling Method (FVSM), Higuchi method, rescaled range (R/S) and a generalized method have been applied to calculate the scaling exponents and fractal dimensions of the time series. Autocorrelation function (ACF) is used to find autoregressive (AR) process and Partial autocorrelation function (PACF) has been used to get the order of AR model. Finally a best fit model has been proposed using Yule-Walker Method with supporting results of goodness of fit and wavelet spectrum. The results reveal an anti-persistent, Short Range Dependent (SRD), self-similar property with signatures of non-causality, non-stationarity and nonlinearity in the data series. The model shows the best fit to the data under observation.     

Stochastic particle acceleration by the forced interaction of relativistic current sheets

We address the problem of interacting relativistic current sheets in self-consistent kinetic plasma simulations within the framework of the Particle-In-Cell model. The interaction is enforced in head-on collisions of up to 10 current sheets at relativistic bulk speeds. The simulations are motivated by the general problem of Poynting flux dissipation in ‘striped wind’ configurations presumably governing the relativistic outflows pervasive in pulsar winds and gamma-ray bursts. We identify the generation of non-thermal particles and formation of a stable power-law shape in the particle energy distributions f(γ) dγ ∝ γ^−s dγ. In 1D, a spectral index s ∼ 2 is observed and attributed to a stochastic Fermi-type acceleration mechanism. In 2D, the generic index of s ∼ 3–4 is retained as in previous simulations of individual current sheets. Whereas in 2D the high energy cut-off is constrained by the limited dissipation of magnetic energy, in 1D the process converts the bulk motion of current sheets towards directed particle momentum of an exclusive class of non-thermal particles.     

Development of a gas chromatography compatible Sample Processing System (SPS) for the in-situ analysis of refractory organic matter in martian soil: preliminary results

In the frame of the 2009 Mars Science Laboratory (MSL) mission a new sample preparation system (SPS) compatible with gas chromatography–mass spectrometry (GC–MS) has been developed for the in situ analysis of complex organic molecules in the Martian soil. The goal is to detect, if they exist, some of the key compounds that play an important role in life on Earth including carboxylic acids, amino acids and nucleobases.     

基于LuGre模型的电液加载系统摩擦补偿

为了提高电液加载系统控制精度,针对摩擦问题提出了基于LuGre摩擦模型的前馈补偿方法.建立了用于摩擦仿真分析和补偿器设计的电液加载系统数学模型;通过实验获取并分析了相关的摩擦数据;基于实验数据进行LuGre模型参数辨识,把LuGre模型和辨识结果引入电液加载系统数学模型,并进行仿真结果与实际摩擦数据的对照,证明了LuGre摩擦模型的准确性.设计前馈补偿器,进行了实验对比,实验结果表明前馈补偿器可将摩擦产生的控制误差有效地降至未补偿时的30%左右.      

Concept options for the aerial survey of Titan

Various aerial platforms intended for long endurance survey of the Titan surface are presented. A few novel concepts are introduced, including a heated methane balloon and a balloon with a tethered wind turbine. All the concept options are predicted to have lower scientific payload fractions than the Huygens probe. It is concluded that the selection of the best aerial platform option depends on more accurate mass estimates and a clear decision on whether, or not, in situ surface composition measurements are required in conjunction with aerial remote sensing.     

Heterogeneous solid/gas chemistry of organic compounds related to comets,meteorites, Titan,and Mars: Laboratory and in lower Earth orbit experiments

To understand the evolution of organic molecules involved in extraterrestrial environments and with exobiological implications, many experimental programs in the laboratory are devoted to photochemical studies in the gaseous phase as well as in the solid state. The validity of such studies and their applications to extraterrestrial environments can be questioned as long as experiments conducted in space conditions, with the full solar spectrum, especially in the short wavelength domain, have not been implemented. The experiments that are described here will be carried out on a FOTON capsule, using the BIOPAN facility, and on the International Space Station, using the EXPOSE facility. Vented and sealed exposition cells will be used, which will allow us to study the chemical evolution in the gaseous phase as well as heterogeneous processes, such as the degradation of solid compounds and the release of gaseous fragments.     

CoRoT and Kepler results: Solar-like oscillators

The space-borne observatories CoRoT (Convection Rotation and planetary Transits) and Kepler have provided photometric time series data of unprecedented precision for large numbers of stars. These data have revolutionized the fields of transiting exoplanets and asteroseismology. In this review some important asteroseismic results obtained using data from the CoRoT and Kepler space missions concerning stars that show solar-like oscillations are discussed. These results comprise, among others, measurements of the location of the base of the convection zone and helium second-ionization zone in main-sequence stars, the presence (or not) of core-helium burning in red-giant stars, as well as differential rotation in these stars.     

Return to Europa: Overview of the Jupiter Europa orbiter mission

Missions to explore Europa have been imagined ever since the Voyager mission first suggested that Europa was geologically very young. Subsequently, the Galileo spacecraft supplied fascinating new insights into this satellite of Jupiter. Now, an international team is proposing a return to the Jupiter system and Europa with the Europa Jupiter System Mission (EJSM). Currently, NASA and ESA are designing two orbiters that would explore the Jovian system and then each would settle into orbit around one of Jupiter’s icy satellites, Europa and Ganymede. In addition, the Japanese Aerospace eXploration Agency (JAXA) is considering a Jupiter magnetospheric orbiter and the Russian Space Agency is investigating a Europa lander.     

HELIO: The Heliophysics Integrated Observatory

Heliophysics is a new research field that explores the Sun–Solar System Connection; it requires the joint exploitation of solar, heliospheric, magnetospheric and ionospheric observations.     

Radioactivity of the Moon and planets

In this report the main results of the study of radioactivity of the solar sistem bodies are considered. The radioactivity of the Moon and planets was measured by means of vehicles in situ. The radioactivity of the lunar samples, brought to the Earth was studied with laboratory equipment.