高速太阳风中α粒子分布的形成

以多级波粒相互作用模型和1维电磁混合模拟方法研究了高速太阳风中α粒子分布的形成机制．认为α粒子从其产生区到1AU,经历4个特征区域：在冕洞下方的小尺度磁重联区,α粒子产生并得到加速：在约十几个太阳半径日冕区,α粒子形成球壳分布函数：在几十个太阳半径处,在Alfven波和温度各向异性不稳定性的作用下,α粒子分布函数演化为漂移Maxwell分布：当α粒子进入0．3－1AU时,Alfven波的作用使α粒子速度超过太阳风速度约1个局域Alfven速度．     

太阳风中动力论Alfven波湍流谱(b)二次激发

根据行星际Alfven湍流是由动力论Alfven波集合形成的模型理论。将行星际Alfven湍流分为三个区域:湍流耗散区、二次激发区和湍流惯性区。并对各区湍流谱的特性分别给出解释。由动力论Alfven波的二次激发和衰减,解释了太阳风高速流质子温度高于电子的事实。      

太阳风中的Alfven波耗散与电子和质子温度分布问题

根据动力论Alfven波耗散机制,详细计算了动力论Alfven波衰减的能量分配给质子和电子的比率.初步解释了高速太阳风中质子温度比电子温度高的事实,定性说明了r＜10R_s时电子快速冷却的原因.      

有限β等离子体中密度和磁场不均匀驱动的动理学Alfven波

在分析有限β等离子体中的密度、磁场不均匀引起的漂移波不稳定性的基础上，剖析了漂移波不稳定性对动理学Alfven波激发的作用．动理学理论能正确地处理有限拉莫半径效应和波粒共振相互作用，本文根据带电粒子在电磁场中的运动特性，采用Vlasov方程描述离子运动，运用漂移动理学方程对电子运动进行描述．密度不均匀和磁场不均匀对产生漂移不稳定性的对比分析表明：在有限β等离子体中，密度不均匀比磁场不均匀更易激发漂移不稳定性，且密度不均匀激发漂移不稳定性中的能量转换和转移更为强烈．这种能量的转换为动理学Alfven波的激发提供了物理基础．所得数值解表明：动理学Alfven波在磁层中能广泛地被激发产生，特别是在磁层空间的极尖区、磁层顶和等离子体片边界层等具有明显的不均匀性区域中更容易被激发产生．本文的研究结果进一步表明动理学Alfven波对磁层空间中能量传输具有重要作用．     

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。      

太阳风中的动力论Alfven激波

本文指出因动力论Alfven波的存在非线性作用，从而能引起波连续陡化;这种情况下考虑频散效应，理论上应该形成中间激波.针对这一物理思想，在二元流体模型下，引进离子声反常阻尼，数值解出中间激波的结构.     

离子非线性极化漂移对动力学Alfvén孤波特性的影响

考虑离子极化漂移中非线性项对动力学Alfven孤波特性的影响，采用双流体模型研究磁化等离子体中低频动力学Alfven稀疏型孤波的特性，所得的结果表明，两种类型的动力学Alfven稀疏型孤波在磁层中大范围内均存在（参数β约为10^-6,0,1,β为等离子体的热压之磁压之比，即β＝20μ0nT/B0^2)，它们或以超Alfven速或以亚Alfven速传播。同时发现在β值较小（10^-6-10^-4)时，离子极化漂移非线性项对动力学Alfven孤波特性有较大的影响，不可忽略，而在较大值时（β－0．1），此修正作用不大，由于动力学Alfven孤波允许平行电场存在，故它对等离子体中带电粒子的加速和能化起重要作用。同时也对离子的横向加速有一定的作用，它使一种新的能量转换机制成为可能。     

高频Alfven波供能的日冕及太阳风模型

空间探测的最新结果表明，太阳大气中广泛存在小尺度喷发事件，这些事件被认为是由新浮现磁通量导致的小尺度磁重联的表现．小尺度磁重联同时会产生高频Alfven波．本文给出了建立在上述思想基础上的描述日冕加热及太阳风加速的时变二元流体模型的一组数值解，显示解的时间演化、收敛特性及守恒特性．在对由过渡区发出的高频Alfven波频谱的适当假设下，数值解能够解释日冕及太阳风等多方面的观测结果，包括日冕加热，极冕洞密度径向变化，太阳风近日冕底部加速，及在03AU观测到的高速流特征．     

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.      

磁重联区Alfven波及新生离子的加速

利用二维混合数值模拟研究了有速度驱动、低等离子体β值情况下的磁场重联过程，结果表明磁重联过程可以产生Alfven波，该Alfven波动对重新区中的新生离子作用，使得新生离子经历投掷角散射方程，具有球壳分布特征，部分新生离子得到加速，其获得的最大能量约为4（miVA0^2/2)，此加速过程所需的加速时间在100／Ωi量级，是一个极快的加速机制，加速粒子能谱为双幂律谱。     

Learning in an immersive digital theater

The Houston Museum of Natural Science, in collaboration with Rice University has an outreach program taking portable digital theaters to schools and community sites for over five years and has conducted research on student learning in this immersive environment. By using an external independent evaluator, the effectiveness of NASA-funded Education and Public Outreach (EPO) projects can be assessed. This paper documents interactive techniques and learning strategies in full-dome digital theaters. The presentation is divided into Evaluation Strategies and Results and Interactivity Strategies and Results. All learners from grades 3–12 showed statistically significant short-term increase in knowledge of basic Earth science concepts after a single 22-min show. Improvements were more significant on items that were taught using more than one modality of instruction: hearing, seeing, discussion, and immersion. Thus immersive theater can be an effective as well as engaging teaching method for Earth and Space science concepts, particularly those that are intrinsically three-dimensional and thus most effectively taught in an immersive environment. The portable system allows taking the educational experience to rural and tribal sites where the underserved students could not afford the time or expense to travel to museums.     

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.     

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.     

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.     

The ESA scientific programme

The ESA scientific programme has, so far, provided several significant astrophysics experiments and further important missions are scheduled for execution during the next decade. These missions are briefly summarised together with several astrophysics investigations presently under study.     

应用于毫米波反射计的多项式校准方法

为了在毫米波波段准确测量波导器件的反射系数,提出了一种应用在反射系数测试前端(反射计)中的校准方法.该校准方法采用基于多项式的误差模型,使得每一个误差项的求解都转化成一个求解轨迹圆圆心的问题,同时不影响求解精度.采用一个滑动负载、一个滑动短路和一个短路器,在毫米波波段降低了对标准件理想程度的要求.实验中搭建了一个Ka波段的反射计,图解误差项的求解过程,分析了误差项的物理意义.把校准后的测量结果与商用矢量网络分析仪(VNA,Vector Network Analyzer)进行比较,吻合较好.同样比较了一组W波段反射计对波纹喇叭的测量结果,进一步验证了方法的合理性.