Element Separation in the Chromosphere Ionization-Diffusion Models for the FIP-Effect

Ionization-diffusion mechanisms to understand the first ionization potential (FIP) fractionation as observed in the solar corona and the solar wind are reviewed. The enrichment of the low-FIP elements (<10 eV) compared to the high-FIP elements, seen in e.g. slow and fast wind or polar plumes, is explained. The behaviour of the heavy noble gases becomes understandable. The absolute fractionation, i.e. in relation to hydrogen, can be calculated and fits well to the measurements. The theoretical velocity-dependence of the fractionation will with used to determine the velocities of the solar wind in the chromosphere. This revised version was published online in June 2006 with corrections to the Cover Date.     

Composition Variations in the Solar Corona and Solar Wind

Order of magnitude variations in relative elemental abundances are observed in the solar corona and solar wind. The instruments aboard SOHO make it possible to explore these variations in detail to determine whether they arise near the solar surface or higher in the corona. A substantial enhancement of low First Ionization Potential (FIP) elements relative to high FIP elements is often seen in both the corona and the solar wind, and that must arise in the chromosphere. Several theoretical models have been put forward to account for the FIP effect, but as yet even the basic physical mechanism responsible remains an open question. Evidence for gravitational settling is also found at larger heights in quiescent streamers. The question is why the heavier elements don't settle out completely. This revised version was published online in June 2006 with corrections to the Cover Date.     

The Lower Solar Atmosphere Rapporteur Paper II

This “rapporteur” report discusses the solar photosphere and low chromosphere in the context of chemical composition studies. The highly dynamical nature of the photosphere does not seem to jeopardize precise determination of solar abundances in classical fashion. It is still an open question how the highly dynamical nature of the low chromosphere contributes to first ionization potential (FIP) fractionation. This revised version was published online in June 2006 with corrections to the Cover Date.     

Nickel Isotopic Composition and Nickel/Iron Ratio in the Solar Wind: Results from SOHO/CELIAS/MTOF

Using the Mass Time-of-Flight Spectrometer (MTOF)—part of the Charge, Elements, Isotope Analysis System (CELIAS)—onboard the Solar Heliospheric Observatory (SOHO) spacecraft, we derive the nickel isotopic composition for the isotopes with mass 58, 60 and 62 in the solar wind. In addition we measure the elemental abundance ratio of nickel to iron. We use data accumulated during ten years of SOHO operation to get sufficiently high counting statistics and compare periods of different solar wind velocities. We compare our values with the meteoritic ratios, which are believed to be a reliable reference for the solar system and also for the solar outer convective zone, since neither element is volatile and no isotopic fractionation is expected in meteorites. Meteoritic isotopic abundances agree with the terrestrial values and can thus be considered to be a reliable reference for the solar isotopic composition. The measurements show that the solar wind elemental Ni/Fe-ratio and the isotopic composition of solar wind nickel are consistent with the meteoritic values. This supports the concept that low-FIP elements are fed without relative fractionation into the solar wind. Our result also confirms the absence of substantial isotopic fractionation processes for medium and heavy ions acting in the solar wind.     

The Structure of the Chromosphere Properties Pertaining to Element Fractionation

We review the structure and dynamics of the solar chromosphere with emphasis on the quiet Sun and properties that are relevant to element fractionation mechanisms. Attention is given to the chromospheric magnetic field, its connections to the photosphere, and to the dynamical evolution of the chromosphere. While some profound advances have been made in the “unmagnetized” chromosphere, our knowledge of the magnetically controlled chromosphere, more relevant for the discussion of element fractionation, is limited. Given the dynamic nature of the chromosphere and the poorly understood magnetic linkage to the corona, it is unlikely that we will soon know the detailed processes leading to FIP fractionation. This revised version was published online in June 2006 with corrections to the Cover Date.     

FIP Fractionation: Theory

In this review, the main models of ion-neutral frationation leading to an enhancement of the low FIP to high FIP abundance ratio in the corona or in the solar wind, are presented. Models based on diffusion parallel to the magnetic field are discussed; they are highly dependent on the boundary conditions. The magnetic field, that naturally separates ions from neutrals moving perpendicular to the field lines direction, when the ion-neutral frequency becomes lower than the ion gyrofrequency, is expected to play an active role in the ion-neutral separation. It is then suggested that ion-neutral fractionation is linked to the formation of the solar chromosphere, i.e. in magnetic flux-tubes at a temperature between 4000 and 6000 K. This revised version was published online in June 2006 with corrections to the Cover Date.     

Element and Isotopic Fractionation in Closed Magnetic Structures

Recent papers have suggested that the slow solar wind is a super-position of material which is released by reconnection from large coronal loops. This reconnection process is driven by large-scale motions of solar magnetic flux driven by the non-radial expansion of the solar wind from the differentially rotating photosphere into more rigidly rotating coronal holes. The elemental composition of the slow solar wind material is observed to be fractionated and more variable than the fast solar wind from coronal holes. Recently, it has also been reported that fractionation also occurs in 3He/4He. This may be interpreted in the frame-work of an existing model for fractionation on large coronal loops in which wave-particle interactions preferentially heat ions thereby modifying their scale-heights. This revised version was published online in June 2006 with corrections to the Cover Date.     

轴流叶片非接触式模态特性测试系统的开发与研究

基于涡轮螺旋桨发动机安装节拉杆系统，对各拉杆的受力状态进行分析，推导拉杆系统力学方程，并得到拉杆之间的力 学关系，结果显示各拉杆所受拉力比值为常数，该常数仅取决于拉杆的尺寸、安装角度、材料参数等。基于ANSYS Workbench 建立拉 杆系统有限元模型，对该系统进行静力学分析得到拉杆应变随拉力的变化关系,并得到不同拉杆拉力之间的关系，数值仿真结果与 理论分析结论相互印证。为基于安装节拉杆的涡桨发动机飞行拉力测量奠定技术基础。     

涡桨发动机安装节拉杆系统力学分析

基于涡轮螺旋桨发动机安装节拉杆系统,对各拉杆的受力状态进行分析,推导拉杆系统力学方程,并得到拉杆之间的力学关系,结果显示各拉杆所受拉力比值为常数,该常数仅取决于拉杆的尺寸、安装角度、材料参数等。基于ANSYS Workbench建立拉杆系统有限元模型,对该系统进行静力学分析得到拉杆应变随拉力的变化关系,并得到不同拉杆拉力之间的关系,数值仿真结果与理论分析结论相互印证。为基于安装节拉杆的涡桨发动机飞行拉力测量奠定技术基础。     

Determination of Sulfur Abundance in the Solar Wind

Solar chemical abundances are determined by comparing solar photospheric spectra with synthetic ones obtained for different sets of abundances and physical conditions. Although such inferred results are reliable, they are model dependent. Therefore, one compares them with the values for the local interstellar medium (LISM). The argument is that they must be similar, but even for LISM abundance determinations models play a fundamental role (i.e., temperature fluctuations, clumpiness, photon leaks). There are still two possible comparisons—one with the meteoritic values and the second with solar wind abundances. In this work we derive a first estimation of the solar wind element ratios of sulfur relative to calcium and magnesium, two neighboring low-FIP elements, using 10 years of CELIAS/MTOF data. We compare the sulfur abundance with the abundance determined from spectroscopic observations and from solar energetic particles. Sulfur is a moderately volatile element, hence, meteoritic sulfur may be depleted relative to non-volatile elements, if compared to its original solar system value.     

基于二维厚板模型的波箔片轴承静特性

建立平箔片的二维厚板有限元模型,运用有限单元法和有限差分法耦合求解Reynolds方程和气膜厚度方程,研究了在两个工作转速下气体波箔片轴承在中截面和边缘处最小气膜厚度随轴承承载力变化规律.通过数值仿真对该模型、一维梁模型、二维薄壳模型和文献实验数据进行对比分析,结果表明:在轴承中截面处,3个模型的最小气膜厚度仿真结果都与实验结果符合得很好,但在轴承边缘处,由于二维厚板模型考虑了平箔片的剪切效应,因此其最小气膜厚度比二维薄壳模型的结果更接近实验值,而一维梁模型只考虑轴承圆周方向,因此不能体现气膜厚度沿轴承长度方向的变化规律.通过研究,为分析箔片轴承动力学特性奠定了理论基础.      

Constraints on the FIP Mechanisms from Solar Wind Abundance Data

In the slow solar wind, elements with (first) ionisation potential (FIP) between ∼10 eV and 22 eV are depleted by a factor of about 4 relative to their abundances in the Outer Convective Zone (OCZ), and helium (FIP = 24.5 eV) is further depleted by a factor of ∼1.8. This depletion, called the FIP effect, is much less pronounced in the high speed streams coming out of coronal holes. The systematics of element depletion suggests that the FIP effect is produced at a temperature ∼104 K and that it is controlled by the time of ionisation at the solar surface. At the boundary of the polar coronal holes, the transition from a strong to a weak FIP effect is relatively sharp and coincides with the change in coronal electron temperature, indicating a profound change in coronal as well as chromospheric properties at this boundary. This revised version was published online in June 2006 with corrections to the Cover Date.     

Application of Coolant Diffusion Equation in Numerical Simulation of Flow in Air-cooled Turbines

This article deals with time-averaged coolant diffusion equation in arbitrary, body-fitted coordinates. Schmidt number and Lewis number are used to obtain the mass diffusion coefficient. Other than the existing N-S solver, a new solver for the diffusion equation and the influences of cooling air on the thermal parameters, such as gas constant, constant-pressure specific heat, is established. Capable of simulating the flow of multi component fluid, this solver is used to simulate the flow in air-cooled two-stage turbines. The comparison of test results from the modified solver to those from the traditional N-S solver has evidenced that a marked difference present is in thermal parameters and flow field structure.     

Effect of Stagnation Temperature on the Supersonic Two- Dimensional Plug Nozzle Conception. Application for Air

When the stagnation temperature of a perfect gas increases, the specific heats and their ratio do not remain constant any more and start to vary with this temperature. The gas remains perfect, its state equation remains always valid, except it will name in more calori-cally imperfect gas or gas at High Temperature. The goal of this research is to trace the profiles of the supersonic plug nozzle when this stagnation temperature is taken into account, lower than the threshold of dissociation of the molecules, by using the new formula of the Prandtl Meyer function, and to have for each exit Mach number, several nozzles shapes by changing the value of this temperature. A study on the error given by the PG (perfect gas) model compared to our model at high temperature is presented. The comparison is made with the case of a calorically perfect gas aiming to give a limit of application of this model. The application is for the air.     

The Composition of Interstellar Molecular Clouds

We consider four aspects of interstellar chemistry for comparison with comets: molecular abundances in general, relative abundances of isomers (specifically, HCN and HNC), ortho/para ratios for molecules, and isotopic fractionation, particularly for the ratio hydrogen/deuterium. Since the environment in which the solar system formed is not well constrained, we consider both isolated dark clouds where low mass stars may form and the "hot cores" that are the sites of high mass star formation. Attention is concentrated on the gas phase, since the grains are considered elsewhere in this volume. This revised version was published online in June 2006 with corrections to the Cover Date.     

Oxygen Isotopes in the Solar System

The oxygen three-isotope system has major advantages over the two-isotope systems of hydrogen, carbon, and nitrogen because different fractionation laws govern intraplanetary and interplanetary processes. This permits discriminating between solar nebular processes and parent-body processes. Oxygen isotopes also serve as a sensitive natural tracer for meteorite classification. This revised version was published online in August 2006 with corrections to the Cover Date.     

Loop Models from SOHO Observations

The Coronal Diagnostic Spectrometer (CDS) on SOHO is a grazing/normal incidence spectrograph, aimed to produce stigmatic spectra of selected regions of the solar surface in six spectral windows of the extreme ultraviolet from 150 Å to 785 Å (Harrison et al. 1995). In the present work, CDS, EIT, MDI and Yohkoh observations of active region lops have been analyzed. These observations are part of JOP 54. CDS monochromatic images from lines at different temperatures have been co-aligned with EIT and MDI images, and loop structures have been clearly identified using Fe XVI emission lines. Density sensitive lines and lines from adjacent stages of ionization of Fe ions have been used to measure electron density and temperature along the loop length; these measurements have been used to determine the electron pressure along the loop and test the constant pressure assumption commonly used in loop modeling. The observations have been compared with a static, isobaric loop model (Landini and Monsignori Fossi 1975) assuming a temperature-constant heating function in the energy balance equation. Good agreement is found for the temperature distribution along the loop at the coronal level. The model pressure is somewhat higher than obtained from density sensitive line ratios.     

低含气率影响下圆柱动静压轴承特性分析

为研究低含气率条件下,温度和气泡含量对润滑油黏度的影响,采用涡轮油和氮气制备油气两相流,在不同温度下采集含气率和动力黏度,拟合得到两相流的黏度计算模型。针对带有深浅腔的圆柱动静压轴承,基于拟合的黏度模型,结合有限元法和有限差分法联立求解油膜Reynolds方程、能量方程及两相流等效密度模型,分析了不同偏心率下承载力、摩擦力、端泄流量、刚度、阻尼系数和失稳转速随含气率变化的规律。结果表明:含气率在2.50%以内,含气率越高,黏度值越大;不同偏心率下油膜承载力、摩擦力和动力特性参数均随含气率的增加而增加,端泄流量随含气率的增加而减小;计入两相流的影响使稳定性有所提高,失稳转速最高增幅为9.14%。     

Working Group 4 Report: Composition and Elemental Abundance Variations in the Solar Atmosphere and Solar Wind

This paper contains a summary of the topics treated in the working group on abundance variations in the solar atmosphere and in the solar wind. The FIP bias (overabundance of particles with low First Ionization Potentials over photospheric abundances) in coronal holes and coronal hole associated solar wind amounts to values between 1 and 2. The FIP bias in the slow solar wind is typically a factor 4, consistent with optical observations in streamers. In order to distinguish between different theoretical models which make an attempt to explain the FIP bias, some observable parameters must be provided. Unfortunately, many models are deficient in this respect. In addition to FIP fractionation, gravitational settling of heavy elements has been found in the core of long lived streamers. The so-called electron 'freeze in' temperatures derived from in situ observed ionization states of minor ions in the fast wind are significantly higher than the electron temperatures derived from diagnostic line ratios observed in polar coronal holes. The distinction between conditions in plumes and interplume lanes needs to be further investigated. The 'freeze in' temperatures for the slow solar wind are consistent with the electron temperatures derived for streamers. This revised version was published online in June 2006 with corrections to the Cover Date.     

Simulation of mass and heat transfer in liquid hydrogen tanks during pressurizing

In order to accurately predict the heat and mass transfer behaviors and analyze key factors affecting pressurization process in the hydrogen tank, a comprehensive 2 D axial symmetry Volume-Of-Fluid(VOF) model is established by Computational Fluid Dynamics(CFD) method.The effects of phase change, turbulence and mass diffusion are included in the model and relationships between physical properties and temperature are also comprehensively considered. The phase change model is based on Hertz-Knudsen equation and the mass transfer time relaxation factor is determined by the NASA's experimental data. The mass diffusion model is included in gaseous helium pressurizing. The key factors including the inlet temperature, inlet mass flow rate, injector types and pressurizing gas kinds are quantitatively analyzed. Compared with the experiment, the simulation results show that the deviation of pressurizing gas mass consumption, condensing mass and ullage temperature are 3.0%, 7.5% and 4.0% respectively. The temperature stratification is existed along the axial direction in the surface liquid region and the ullage region, and the bulk liquid is in subcooled state during pressurizing. The location of phase change mainly appears near the vapor–liquid interface, and the mass transfer expressing as condensation or vaporization is mainly determined by the heat convection and molecular concentration near the vapor–liquid interface.The key factors show that increasing the inlet temperature and inlet mass flow rate could shorten the pressurizing time interval and save the pressurizing gas mass. The proportion of the total energy addition of the tank absorbed by the ullage region, the liquid region and the tank wall respectively is greatly influenced by the injector types and more heat transferred into the ullage would result in a faster pressure rising rate. Gaseous hydrogen pressurization has a higher efficiency than gaseous helium pressurization. The simulation results presented in this paper can be used as a reference for design optimization of the pressurization systems of cryogenic liquid launch vehicles so as to save the mass of pressurizing gases and shorten the pressurizing time interval.