Energetic particles at high latitudes

We review work on diffusion coefficients of energetic particles with an attempt to extract implications on their behaviour at high latitudes. In the ecliptic plane results from solar energetic particle propagation between the Sun and about 5 AU can be described by an effective radial mean free path _r which is approximately constant as a function of distancer. When particle propagation in three dimensions in the heliosphere is considered it is not sufficient to consider _r only. Jovian electrons can be used as probes to determine the parameters of three-dimensional diffusion. In the polar regions diffusion is dominated by its parallel component. Some predictions how should vary with latitude are discussed. For different choices of this variation we present expectations for intensity-time profiles of solar particle events during the Ulysses polar passages.     

The Cassini Cosmic Dust Analyzer

The Cassini-Huygens Cosmic Dust Analyzer (CDA) is intended to provide direct observations of dust grains with masses between 10⁻¹⁹ and 10⁻⁹ kg in interplanetary space and in the jovian and saturnian systems, to investigate their physical, chemical and dynamical properties as functions of the distances to the Sun, to Jupiter and to Saturn and its satellites and rings, to study their interaction with the saturnian rings, satellites and magnetosphere. Chemical composition of interplanetary meteoroids will be compared with asteroidal and cometary dust, as well as with Saturn dust, ejecta from rings and satellites. Ring and satellites phenomena which might be effects of meteoroid impacts will be compared with the interplanetary dust environment. Electrical charges of particulate matter in the magnetosphere and its consequences will be studied, e.g. the effects of the ambient plasma and the magnetic field on the trajectories of dust particles as well as fragmentation of particles due to electrostatic disruption.The investigation will be performed with an instrument that measures the mass, composition, electric charge, speed, and flight direction of individual dust particles. It is a highly reliable and versatile instrument with a mass sensitivity 10⁶ times higher than that of the Pioneer 10 and 11 dust detectors which measured dust in the saturnian system. The Cosmic Dust Analyzer has significant inheritance from former space instrumentation developed for the VEGA, Giotto, Galileo, and Ulysses missions. It will reliably measure impacts from as low as 1 impact per month up to 10⁴ impacts per second. The instrument weighs 17 kg and consumes 12 W, the integrated time-of-flight mass spectrometer has a mass resolution of up to 50. The nominal data transmission rate is 524 bits/s and varies between 50 and 4192 bps.This revised version was published online in July 2005 with a corrected cover date.     

喷流对飞机尾流涡影响的试验研究

飞机产生的尾流涡,特别是大尺度的翼尖涡,对尾随其后的飞行器是非常有害的,本文旨在探索利用飞机发动机产生的喷流加速尾流涡消亡的方法。试验采用简化的飞机模型(有尾翼),建立了包含一对翼尖涡及一对反向旋转的尾翼涡(通过以负迎角安装尾翼得到)的4涡尾流系统。在无外来扰动的情况下,不同的尾翼设置下得到的尾翼涡对翼尖涡的作用效果不同,有的能导致翼尖涡提前消亡,有的则不能。考察了不同强度的喷流对不同4涡尾流系统的影响,且作为对比,对无尾翼(2涡系统)及无喷流下的各种情况也分别作了观测。试验在拖曳水槽中进行,运用体视粒子图像测速(SPIV)技术,观测了与模型拖曳方向垂直的、从机翼后缘到下游约45翼展间均布的一系列切面。结果表明:当喷流直接作用于涡时,其效果主要取决于两者之间的初始距离及相对强度;而当喷流作用于整个4涡尾流系统时,其引入的扰动对不同的系统均能起到一定程度的改善作用,这种作用的关键在于利用喷流优化对翼尖涡进行扰动的机制,而不仅仅取决于喷流的强度。     

Millimeter wave radiation sources visible in solar corona

Coronal millimeter wave sources (CMMS) have been observed at radio frequencies 22–90 GHz (at wavelengths 3–13 mm). The observed CMMS have been classified into three different categories according to their time scale and relation to other wave-length events. The CMMS indicate enhancement of electron density in the corona, as well as magnetic loop structures. The CMMS are evidence of dynamical processes taking place at the lower levels of the corona, propagating into the higher levels.     

Net electric power of concentrating solar mirror systems for application in space as a function of the distance to the sun

The use of solar radiation by means of concentrating solar mirror systems, such as parabolic and spheric configurations, mainly is an engineering problem. A decisive characteristic for the optimisation of a complete system with turboelectric power conversion is the thermal cycle applied. Besides the Carnot process, here taken up into the study as an ideal comparative process, suitable processes for the technological realisation are the Brayton process and the Rankine process. The Brayton process is a typical gas turbine process using only the gaseous phase. The Rankine process is a steam engine process using liquid and gaseous phase.The work in hand shows how such solar systems with turboelectric conversion are optimised with respect to their specific weight (kg/kW_e) and how the distance to the sun as well as technological data enter into the analysis.As expected, the Carnot cycle as an ideal comparative process for both types of systems shows the best results for the optimum specific mass of the system. Regarding the real processes, the Rankine cycle shows more favourable characteristics than the Brayton cycle. The difference of the specific masses of the real processes mainly results from the different thermal conditions at the radiator.The influence of the distance to the sun is as expected. The nearer to the sun the solar power system operates, the better is the optimum specific mass of the system. For distances to the sun between 0.3 and 1.0 AU the spheric system shows a better behaviour than the parabolic system. For distances to the sun greater than 2.0 AU the parabolic system shows better behaviour of the specific weight. In the region between 1 and 2 AU the better optimum specific mass of the system belongs to the technological data used in the analysis.     

Comparison of nuclear and solar power plants with turboelectric generators for application in space

The aim of the analysis is to determine and to compare the specific mass of nuclear and solar power plants for application in space depending on technological data as well as on data subject to the mission.On the basis of the known theory of Ruppe and Blumenberg[1–3], nuclear power plants with turboelectric generators as well as solar-thermal power plants with parabolic or spheric mirrors are being analysed. The following thermodynamic processes are applied: the Rankine process, the Brayton process and—as an ideal comparative process—the Carnot process. An important parameter of the analysis for nuclear power plants is the net electric power, for the solar-thermal power plant the distance to the sun is of importance.     

How to evidence Primitive Life on an exo-Planet? — The DARWIN project

We report the concept of an IR observatory, with interferometric rejection, to search for Primitive Life on an extra-Solar Planet which has been proposed to the European Space Agency.     

液氧/煤油发动机地面试验故障紧急关机系统研制

论述了液氧／煤油发动机研制地面试车中，出现故障时所采用的紧急关机系统的原理和系统结构、设计程序、设计指标、关机判断准则、验证及应用等。     

Magnetic Field Amplification in Galaxy Clusters and Its Simulation

We review the present theoretical and numerical understanding of magnetic field amplification in cosmic large-scale structure, on length scales of galaxy clusters and beyond. Structure formation drives compression and turbulence, which amplify tiny magnetic seed fields to the microGauss values that are observed in the intracluster medium. This process is intimately connected to the properties of turbulence and the microphysics of the intra-cluster medium. Additional roles are played by merger induced shocks that sweep through the intra-cluster medium and motions induced by sloshing cool cores. The accurate simulation of magnetic field amplification in clusters still poses a serious challenge for simulations of cosmological structure formation. We review the current literature on cosmological simulations that include magnetic fields and outline theoretical as well as numerical challenges.