Supersonic steady accretion of a rotating cold “Iron Gas” onto a neutron star after gravitational collapse     

V. S. Imshennik  M. S. Popov 《Astronomy Letters》2001,27(2):81-90

We analytically generalize the well-known solution of steady supersonic spherically symmetric gas accretion onto a star (Bondi 1952) for an iron atmosphere with completely degenerate electrons with an arbitrary degree of relativity. This solution is used for typical physical conditions in the vicinity of protoneutron stars produced by gravitational collapse with masses M ₀=(1.4?1.8)M _⊙ and over a wide range of nonzero “iron gas” densities at infinity, ρ_∞=(10⁴?5×10⁶)g cm^?3. Under these conditions, we determine all accretion parameters, including the accretion rate, whose value is ～(10?50)M _⊙s^?1 at M ₀=1.8M _⊙ (it is a factor of 1.7 lower for M ₀=1.4M _⊙, because the accretion rate is exactly ∝M ₀ ² ). We take into account the effect of accreting-gas rotation in a quasi-one-dimensional approximation, which has generally proved to be marginal with respect to the accretion rate.  相似文献   

Low frequency waves in plasmas with spatially varying electron temperature     

P. Guio  S. Børve  H. L. Pécseli  J. Trulsen 《Annales Geophysicae》2001,18(12):1613-1622

Low frequency electrostatic waves are studied in magnetized plasmas with an electron temperature which varies with position in a direction perpendicular to the magnetic field. For wave frequencies below the ion cyclotron frequency, the waves need not follow any definite dispersion relation. Instead a band of phase velocities is allowed, with a range of variation depending on the maximum and minimum values of the electron temperature. Simple model equations are obtained for the general case which can be solved to give the spatial variation of a harmonically time varying potential. A simple analytical model for the phenomenon is presented and the results are supported by numerical simulations carried out in a 2.5-dimensional particle-in-cell numerical simulation. We find that when the electron temperature is striated along B₀ and low frequency waves (_ci) are excited in this environment, then the intensity of these low frequency waves will be striated in a manner following the electron temperature striations. High frequency ion acoustic waves (_ci) will on the other hand have a spatially more uniform intensity distribution.  相似文献   

On determining the noon polar cap boundary from SuperDARN HF radar backscatter characteristics     

M. Pinnock  A. S. Rodger 《Annales Geophysicae》2001,18(12):1523-1530

Previous work has shown that ionospheric HF radar backscatter in the noon sector can be used to locate the footprint of the magnetospheric cusp particle precipitation. This has enabled the radar data to be used as a proxy for the location of the polar cap boundary, and hence measure the flow of plasma across it to derive the reconnection electric field in the ionosphere. This work used only single radar data sets with a field of view limited to 2 h of local time. In this case study using four of the SuperDARN radars, we examine the boundary determined over 6 h of magnetic local time around the noon sector and its relationship to the convection pattern. The variation with longitude of the latitude of the radar scatter with cusp characteristics shows a bay-like feature. It is shown that this feature is shaped by the variation with longitude of the poleward flow component of the ionospheric plasma and may be understood in terms of cusp ion time-of-flight effects. Using this interpretation, we derive the time-of-flight of the cusp ions and find that it is consistent with approximately 1 keV ions injected from a subsolar reconnection site. A method for deriving a more accurate estimate of the location of the open-closed field line boundary from HF radar data is described.  相似文献   

电感耦合等离子体发射光谱法测定高铁三水铝土矿中的主量和次量元素     

黄肇敏  崔萍萍  周素莲 《矿产与地质》2007,21(4):476-478

采用电感耦合等离子体发射光谱法,同时测定高铁三水铝土矿中的Si、Fe、Al、Ti、Mn、V、As、P等元素。对影响其光谱测量的各种因素进行了较为详细的研究,确定了最佳的试验测定条件。结果表明,该方法的检出限为0.0012-0.061μg/mL,回收率为95.4%-107.4%,主量元素相对标准偏差在1%-3%之间,次量元素相对标准偏差在2%-6%之间。该方法准确、快速、简便,应用于高铁三水铝土矿的测定,结果令人满意。  相似文献   

电感耦合等离子体原子发射光谱法测定黄铁矿中微量元素   总被引：5，自引：7，他引：5  

常平  王松君等 《岩矿测试》2002,21(4):304-306

采用电感耦合等离子体原子发射光谱法检测了黄铁矿中Cd,Co,Cu,Mn,Pb,Zn和Ni。用干扰系数校正法消除黄铁矿中铁对上述元素的干扰，采用HCl-HNO3体系溶解矿样，不需化学分离，直接测定。方法已应用于国家标准物质GBW07267的测定。结果与标准值相符，相对标准偏差（n=8)为1.5%-7.3%。  相似文献   

地幔流体及其成矿作用   总被引：8，自引：0，他引：8  

胡圣虹  胡兆初  刘勇胜  罗彦  林守麟  高山 《地学前缘》2001,8(4):0-0

高灵敏度、高精密度、低检出限、多元素同时检测并可提供同位素组成比值信息的等离子体质谱与高空间分辨率的紫外激光采样技术结合 ,可定量地测定单个流体包裹体中常、微量元素含量 ,为成矿流体的研究提供了一个新的研究手段。文中简要地介绍了激光剥蚀电感耦合等离子体质谱 (LA ICP MS)分析仪器的发展 ,结合实验室的研究工作 ,就激光剥蚀池的设计、单个流体包裹体的剥蚀方法、元素的分馏效率、定量校正技术及其在成矿成因物理化学机制研究中的应用等进行评述 ,并阐述单个流体包裹体元素组成的LA ICP MS分析技术存在的局限和发展趋势。  相似文献   

电感耦合等离子体质谱法同时测定地质样品中痕量碘溴硒砷的研究：Ⅱ.土壤及沉积物标准物质分析   总被引：11，自引：8，他引：11  

李冰  史世云等 《岩矿测试》2001,20(4):241-246

样品用碳酸钠和氧化锌混合熔剂半熔，热水提取，然后用强酸性阳离子交换树脂将阴离子形式存在的分析元素与溶液中大量钠、锌等阳离子分离，采用电感耦合等离子体质谱法直接同时测定溶液中的碘、溴、硒、砷。用0.07mol/L的氨水溶液清洗进样系统，有效减少了碘等元素的记忆效应和清洗时间。方法检出限（10σ，DF=100）溴、碘分别为0.15和0.028μg/g，砷、硒分别为0.04和0.004μg/g。用土壤和沉积物等地质标准物质分析验证了方法的准确度和精密度，绝大多数分析结果在标准值的允许误差范围之内。样品10次测定的RSD为0.8%～2.8%。  相似文献   

Naturally Enhanced Ion-Acoustic Spectra And Their Interpretation     

Francis Sedgemore-Schulthess  Jean-Pierre St. Maurice 《Surveys in Geophysics》2001,22(1):55-92

Incoherent scatter radars are designed to detect scatter from thermalfluctuations in the ionosphere. These fluctuations contain, among other things,features associated with ion-acoustic waves driven by random motions within theplasma. The resulting spectra are generally broad and noisy, but neverthelessthe technique can, through a detailed analysis of spectra, be used to measure arange of physical parameters in the Earth's upper atmosphere, and provides apowerful diagnostic in studies of magnetosphere-ionosphere coupling,thermosphere dynamics and the geospace environment in general. In recent yearsthere has been much interest in naturally occurring (as opposed to artificiallystimulated) enhanced ion-acoustic spectra seen in the auroral zone andcusp/cleft region. A study of the plasma instability processes that lead tosuch spectra will help us to better understand auroral particle acceleration,wave-particle and wave-wave interactions in the ionosphere, and theirassociation with magnetospheric processes. There is now a substantial body ofliterature documenting observations of enhanced ion-acoustic spectra, but thereremains controversy over generation mechanisms. We present a review ofliterature documenting observations of naturally enhanced ion-acoustic spectra,observed mainly along the geomagnetic field direction, along with a discussionof the theories put forward to explain such phenomena.  相似文献   

Trace Elements Analysis of Geological Samples by Laser Ablation Inductively Coupled Plasma Mass Spectrometry     

Luo Yan Liu Yongsheng Hu Shenghong Gao Shan Open Laboratory of Constitution  Interaction  Dynamics of the Crust Mantle System  Ministry of National Lands  Resources  China University of Geosciences  Wuhan Lin Shoulin Faculty of Material Sc 《中国地质大学学报(英文版)》2001,12(3)

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低地球轨道（LEO）的大型航天器充电     

操学俊  徐跃民 《地球物理学进展》1996,11(3):104-108

本文根据ＬＥＯ中等离子体温度低，密度高，德拜长度小的特点，采用薄鞘层近似，计算了离子收集电流；根据电流平衡方程，考虑表面二次电子发射，计算了大型航天器表面在沉降电子流辐照下的充电特性。  相似文献