武汉地区电离层电子浓度总含量的统计经验模式研究

由武汉电离层观象台一个太阳黑子周期（1980-1990年）的实测电离层电子浓度总含量（TEC）资料，统计分析得出了武汉地区的一个TEC经验模式，模式很好地再现了武汉地区的TEC观测值，其预测误差在太阳活动高年稍太，低年较小；在春秋两季稍大，冬夏两季较小；在当地时间白天和傍晚稍大，夜间和早晨较小。此外，与国际参考电离层模式IRI的计算结果比较，本模式预测的TEC值更接近于实际观测结果，同时，本文也初步探讨了TEC的半年变化特征和冬季异常现象。     

武汉地区电离层TEC和NmF2及板厚的季节变化

通过利用武汉电离层观测站(114.4°E,30.6°N)1980-1990年对E8T-Ⅱ卫星信标的法拉第旋转测量的TEC(电子浓度总含量)数据,以及由测高仪测量的1980-1990年间的f0F2(F2层临界频率)数据,研究了武汉地区TEC,NmF2(最大电子浓度)和板厚的季节变化,同时比较了IRI和武汉单站模式在预测NmF2季节性方面的有效性.武汉单站模式在预测NmF2季节性变化方面优于IRI模式.      

电离图分片换算法中谷的处理

本文介绍用电离图的寻常波描迹换算电离层剖面.应用Gulyaeva的经验公式确定F层的底高,E、F层之间的谷电离区的模式等效为一平板层,以Budden的分片解法为基础对F层进行频高换算.用此方法对Herbert提供的几条参考剖面进行了比较,电子浓度所在高度的误差一般不超过±10公里(中纬地区).      

IRI-2007预测TEC在广州地区的适用性分析

利用广州站(23.2°N, 113.3°E) GPS双频接收机监测的电离层TEC数据和IRI-2007模型不同电离层输入参数计算得到的TEC预测值, 对比分析了太阳活动低年(2008年)广州地区TEC的变化特征. 结果表明, TEC观测值周日变化在16:00LT左右达到最大值, 而IRI-TEC最大值出现时间较GPS-TEC提前1h左右. TEC季节变化在春秋分较高, 两至季节较低, 表现出明显的半年特性和季节依赖性, 并出现冬季异常现象. IRI-TEC与GPS-TEC在白天具有较好的一致性, 夜间偏差较大. 不同电离层输入参数得到的TEC预测值也相差较大, 选用顶部电子密度参数NeQuick、底部厚度参数B0 Table并用URSI系数计算F₂层峰值参数时, 能较好地反映TEC观测值的变化特征. 在对磁暴的响应上, 预测值无明显变化, 观测值则有比较明显的表现. 通过对比, 初步分析了利用IRI-2007模型预测TEC在广州地区的适用性, 并给出了合理的参数选择方案.      

不同上边界条件下的极区电离层数值模拟

利用一维自洽的极区电离层模型,研究了沿磁力线方向不同电离层-磁层耦合条件下极区电离层的响应.此模型在110-610km的电离层空间区域内,综合求解描述极区电离层的连续性方程、动量方程和能量方程,以得到电离层数值解.研究发现,上边界条件在200 km以上的高度能显著地影响电离层参量的形态.较高的O+上行速度对应较低的F层峰值和较高的电子温度.不同边界O+上行速度对应的温度高度剖面完全不同.200km以上电子温度高度剖面不但由来自磁层的热流通量所控制,同时还受到场向O+速度的影响.对利用电离层模型研究电离层内部物理过程提出了建议.      

地磁暴期间北半球高纬度地区电离层变化特征及对精密定位的影响

基于加拿大地区高纬度电离层观测网的电离层闪烁观测数据,分析了2018年8月26日地磁暴事件引发的北半球高纬度地区电离层总电子含量(TEC)异常变化、TEC变化率指数(ROTI)及电离层相位闪烁的变化特征.结果表明:加拿大地区最大异常值约6 TECU,磁暴引发全球电离层TEC异常峰值高达20 TECU;加拿大地区电离层相...     

大耀斑期间向日面电离层总电子含量的响应个例分析

利用2001年4月15日1336UT耀斑爆发期间向日面GPS观测数据提取的总电子含量的时间变化曲线。分析了向日面电离层对这次耀斑的响应特点．结果表明，耀斑期间向日面电离层出现了总电子含量突增事件．最大总电子含量增加量约为2．6TECU，在0600LT和1800LT都观测到了总电子含量突增，世增加幅度仅为0．5-1TECU．在高纬地区，由于电离层闪烁，从TEC时间变化曲线提取不出来总电子含量增加值．从各卫星星下点处的TEC增加量和各星下点处的太阳天顶角的关系可以看到，TEC增加量与太阳天顶角有关，太阳天顶角越大，TEC增幅越小。另外，从总电子含量时间变化率曲线上还观测到了时间同步的小尺度扰动，通过与耀斑期间硬X射线辐射通量的比较，发现两者有明显的相关性，电离层中的这种扰动与耀斑期间的硬X射线或远紫外辐射有关．     

利用COSMIC数据构建的全球垂直TEC图的验证研究

在日固坐标系(地磁纬度和地方时)下, 累积地方时过去24h的COSMIC(Constellation Observing System for Meteorology Ionosphere andClimate)观测资料, 通过对110$sim$750km高度范围内的电子密度进行数值积分得到各掩星点的垂直TEC值, 进而利用Kriging方法插值产生近实时的全球地方时MAGLat2.5°×2h的COSMIC TEC图. 利用2008年1月1日至2010年6月30日共30个月的COSMIC数据, 逐日构建COSMICTEC图, 将其与全球导航卫星系统服务组织(International GNSS Service,IGS)发布的全球电离层TEC图(Global Ionospheric Maps, GIMs)以及OSTM/JASON-2卫星高度计观测值分别进行比对,证明利用COSMIC掩星资料构建全球电离层垂直TEC图是可行的.      

全球电离层对2000年4月6-7日磁暴事件的响应

利用分布于全球的电离层台站的测高仪观测数据,对扰动期间,foF2值与其宁静期间参考值进行比较,研究了2000年4月6—7日磁暴期间全球不同区域电离层的响应形态,并通过对比磁扰期间NmF2的变化与由MSISR90经验模式估算的中性大气浓度比(no／nN2)的变化,探讨了本次事件期间的电离层暴扰动机制．结果表明,在磁暴主相和恢复相早期,出现了全球性的电离层F2层负相暴效应．最大负相暴效应出现在磁暴恢复相早期,即电离层暴恢复相开始时间滞后于磁暴恢复相开始时间．在磁暴恢复相后期,一些台站出现正相扰动．研究结果表明,本次事件期间的电离层暴主要是由磁暴活动而诱发的热层暴环流引起的．     

太阳活动下降年昆明地区TEC变化特征与IRI-2020模拟比较分析

利用昆明低纬度测站（24.7°N,102.9°E，磁纬15.1°N）2016-2019年的观测数据和最新版的国际参考电离层（IRI-2020）模拟结果，对昆明地区电离层总电子含量（TEC）在太阳活动下降年期间的变化特征及与模型输出进行对比研究。结果表明,昆明TEC存在明显的春秋高值、夏冬低值的半年异常；白天高值、夜间低值的日变化特点突出，日峰值出现在06:30-08:00 UT（约13:00-15:00 LT）;TEC随太阳活动减弱而明显下降，年平均峰值在2016-2019年分别为48,33,27,24 TECU；日峰值TEC与F10.7存在显著相关，月均值相关系数达到0.86，而与Ap指数则表现为弱相关；IRI-2020能较好地模拟昆明地区TEC的季节变化，但与观测值存在较大差异；均方根偏差值多集中在2～15 TECU，相对偏差百分比值主要在–85%～50%范围变化。对比结果表明IRI-2020的预测精度仍有待提高。     

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.      

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.     

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.     

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.     

清镇陨石（EH3）中陨硫钙石的REE微量元素及成因意义

本文运用INAA分析了14个清镇陨石中陨硫钙石单矿物颗粒的难熔元素(La、Ce、Sm、Eu、Yb、Lu、Ca、Sc、Hf和Th),挥发性元素(Na、Cr、Zn、Se、Br等)和亲铁元素(Fe、Ni、Co、Ir、Au、As)含量。结果表明陨硫钙石高度富集难熔亲石元素,是顽火辉石陨石中REE的主要载体,携带了约80％的全岩REE总量。相对于HREE,LREE有更大的富集程度,而且早期凝聚的颗粒较晚期凝聚的颗粒更富集REE,同时陨硫钙石富集挥发性元素Se、Br等。清镇陨硫钙石的微量元素特征揭示了它来自于太阳星云的高温凝聚特征和成因。     

柔性航天器IPACS建模与动力学分析

利用拟坐标下的拉格朗日方程和动量矩定理,建立了带变速控制力矩陀螺群(VSCMGs,Variable Speed Control Moment Gyroscopes)的柔性航天器的能量/姿态一体化控制系统(IPACS, Integrated Power/Attitude Control System)的动力学模型,该模型适合于姿态控制律设计及VSCMGs操纵律设计.采用动量管理和VSCMGs构型选取相结合的方法,有效地避免了VSCMGs设计时可能出现的奇异问题.分析了采用VSCMGs的柔性航天器IPACS中的动力学耦合问题,并以某大型航天器为例进行了数值仿真.分析和仿真结果显示出,当VSCMGs的力矩轴接近(或陷入)奇异或进行储/放能切换时,VSCMGs都会对柔性附件造成显著影响.      

Progress in tropospheric ammonia retrieval from the MIPAS satellite instrument

The Michelson Interferometer for Passive Atmospheric Sounding is a polar orbiting high resolution mid-infrared emission limb sounder with a nominal vertical resolution of 3 km. Work to extend the list of routinely retrieved species led to the examination of ammonia, NH₃. In this paper, we explore the feasibility of upper tropospheric retrievals around 6-km altitude, discussing appropriate methods. We demonstrate a weak north to south gradient outside the error bars, using co-addition to improve signal-to-noise and compare these first results with a model.     

Monitoring spatio-temporal variations in aerosols and aerosol–cloud interactions over Pakistan using MODIS data

Clouds are important elements in climatic processes and interactions between aerosols and clouds are therefore a hot topic for scientific research. Aerosols show both spatial and temporal variations, which can lead to variations in the microphysics of clouds. In this research, we have examined the spatial and temporal variations in aerosol particles over Pakistan and the impact of these variations on various optical properties of clouds, using Moderate Resolution Imaging Spectroradiometer (MODIS) data from the Terra satellite. We used the Hybrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) model for trajectory analysis to reveal the origins of air masses, with the aim of understanding these spatial and temporal variabilities in aerosol concentrations. We also documented seasonal variations in patterns of aerosol optical depth (AOD) over Pakistan, for which the highest values occur during the monsoon season (June–August). We then analyzed the relationships between AOD and four other cloud parameters, namely water vapour (WV), cloud fraction (CF), cloud top temperature (CTT) and cloud top pressure (CTP). Regional correlation maps and time series plots for aerosol (AOD) and cloud parameters were produced to provide a better understanding of aerosol–cloud interaction. The analyses showed strong positive correlations between AOD and WV for all of the eight cities investigated. The correlation between AOD and CF was positive for those cities where the air masses were predominantly humid, but negative for those cities where the air masses were relatively dry and carried a low aerosol abundance. These correlations were clearly dependent on the meteorological conditions for all of the eight cities investigated. Because of the observed AOD–CF relationship, the co-variation of AOD with CTP and CTT may be attributable to large-scale meteorological variations: AOD showed a positive correlation with CTP and CTT in northern regions of Pakistan and a negative correlation in southern regions.     

Technology development for a long duration,mid-cloud level Venus balloon

This paper describes the results of ongoing technology development activities for a Venus spherical superpressure balloon capable of flying for long durations (30 days) in the middle cloud layer at an altitude of 55.5 km. Data is presented from a successful aerial deployment and inflation flight experiment on a 5.5 m diameter prototype balloon conducted at a 2.5 km altitude above the Earth. Although the balloon in that test was not released for free flight, all other steps in the deployment and inflation process were successfully executed. Experimental and computational results are also presented from an investigation of the stress concentration phenomenon at the junction of the metal end fitting and fabric end cap of the prototype Venus balloon. Good agreement was found between the simulation and experimental results and a stress concentration factor of 1.55 determined for this end cap design compared to the expectations of thin membrane theory. Finally, results are presented for a new, second-generation Venus balloon material utilizing Aclar™ film instead of Teflon. Optical property and sulfuric acid tolerance data are presented for this material based on laboratory testing of samples.