Geoeffectivity of Coronal Mass Ejections

Coronal mass ejections and post-shock streams driven by them are the most efficient drivers of strong magnetospheric activity, magnetic storms. For this reason there is considerable interest in trying to make reliable forecasts for the effects of CMEs as much in advance as possible. To succeed this requires understanding of all aspects related to CMEs, starting from their emergence on the Sun to their propagation to the vicinity of the Earth and to effects within the magnetosphere. In this article we discuss some recent results on the geoeffectivity of different types of CME/shock structures. A particularly intriguing observation is that smoothly rotating magnetic fields within CMEs are most efficient in driving storm activity seen in the inner magnetosphere due to enhanced ring current, whereas the sheath regions between the shock and the ejecta tend to favour high-latitude activity.     

An Introduction to Theory and Models of CMEs, Shocks, and Solar Energetic Particles

We present a brief introduction to the essential physics of coronal mass ejections as well as a review of theory and models of CME initiation, solar energetic particle (SEP) acceleration, and shock propagation. A brief review of the history of CME models demonstrates steady progress toward an understanding of CME initiation, but it is clear that the question of what initiates CMEs has still not been solved. For illustration, we focus on the flux cancellation model and the breakout model. We contrast the similarities and differences between these models, and we examine how their essential features compare with observations. We review the generation of shocks by CMEs. We also outline the theoretical ideas behind the origin of a gradual SEP event at the evolving CME-driven coronal/interplanetary shock and the origin of “impulsive” SEP events at flare sites of magnetic reconnection below CMEs. We argue that future developments in models require focused study of “campaign events” to best utilize the wealth of available CME and SEP observations.     

An Introduction to CMEs and Energetic Particles

Energetic particle observations in the interplanetary medium provide fundamental information about the origin, development and structure of coronal mass ejections. This paper reviews the status of our understanding of the ways in which particles are energised at the Sun in association with CMEs. This understanding will remain incomplete until the relationship between CMEs and flares is determined and we know the topology of the associated magnetic fields. The paper also discusses the characteristics of interplanetary CMEs that may be probed using particle observations.     

Coronal Observations of CMEs

CMEs have been observed for over 30 years with a wide variety of instruments. It is now possible to derive detailed and quantitative information on CME morphology, velocity, acceleration and mass. Flares associated with CMEs are observed in X-rays, and several different radio signatures are also seen. Optical and UV spectra of CMEs both on the disk and at the limb provide velocities along the line of sight and diagnostics for temperature, density and composition. From the vast quantity of data we attempt to synthesize the current state of knowledge of the properties of CMEs, along with some specific observed characteristics that illuminate the physical processes occurring during CME eruption. These include the common three-part structures of CMEs, which is generally attributed to compressed material at the leading edge, a low-density magnetic bubble and dense prominence gas. Signatures of shock waves are seen, but the location of these shocks relative to the other structures and the occurrence rate at the heights where Solar Energetic Particles are produced remains controversial. The relationships among CMEs, Moreton waves, EIT waves, and EUV dimming are also cloudy. The close connection between CMEs and flares suggests that magnetic reconnection plays an important role in CME eruption and evolution. We discuss the evidence for reconnection in current sheets from white-light, X-ray, radio and UV observations. Finally, we summarize the requirements for future instrumentation that might answer the outstanding questions and the opportunities that new space-based and ground-based observatories will provide in the future.     

The Hydrogen Exospheric Density Profile Measured with ASPERA-3/NPD

We have evaluated the Lyman-α limb emission from the exospheric hydrogen of Mars measured by the neutral particle detector of the ASPERA-3 instrument on Mars Express in 2004 at low solar activity (solar activity index = 42, F_10.7=100). We derive estimates for the hydrogen exobase density, n _H = 10¹⁰ m^?3, and for the apparent temperature, T > 600 K. We conclude that the limb emission measurement is dominated by a hydrogen component that is considerably hotter than the bulk temperature at the exobase. The derived values for the exosphere density and temperature are compared with similar measurements done by the Mariner space probes in the 1969. The values found with Mars Express and Mariner data are brought in a broader context of exosphere models including the possibility of having two hydrogen components in the Martian exosphere. The present observation of the Martian hydrogen exosphere is the first one at high altitudes during low solar activity, and shows that for low solar activity exospheric densities are not higher than for high solar activity.     

透博梅卡公司探索新的涡轴发动机

虽然透博梅卡公司现在每年销售发动机超过650台,但它们却认为已经到了研制替换轴功率为450～670千瓦级发动机的时候了.     

汽车外表面模型测量数据处理及曲面建模

介绍了车身外形曲面逆向工程的方法,对光学扫描测量得到的点云数据建立了滤波、平滑和去除冗余的自动处理方法,用NURBS自由曲面模型实现了车身曲面重建.这些方法提高了扫描点云数据的处理精度和曲面建模的效率.     

1-3型压电纤维主动叠层板扭转特性的研究

对4类典型铺层的1-3型压电纤维复合材料主动板的变形模式进行了理论分析。在此基础上对具有扭转变形模式的主动叠层板进行了振动特性分析,得到了该类型主动叠层板在外界电场激励下的稳态解。最后对该类主动叠层板的扭转振动特性进行了深入的研究,包括作用电场强度的大小、频率对扭转特性的影响、压电纤维铺层角和压电纤维体积比对主动叠层板扭转特性的影响等。算例表明本文计算模型和有限元得到的结果符合良好,同时算例结果表明含1-3型压电纤维复合材料主动叠层板具有良好的主动扭转特性。     

利用压电驱动器改善飞机横滚性能的试验验证

利用分布粘帖在矩形机翼上下两面的压电驱动器,探索使用该类结构提高飞行器横滚能力的可能性。通过风洞模型设计、材料性能测试、模型固有特性测试、压电柔度矩阵测试等试验项目,保证了有限元模型的计算精度,最终通过模型的风洞试验验证了利用气动弹性效应,获得了附加升力与横滚力矩的方案。该原理性试验说明利用分布式压电驱动器改善横滚性能是可行的。