Dynamics of the plasmasphere in the dusk sector as observed in the outer ionosphere     

J. Bošková  F. Jiříček  J. Šmilauer  P. Tříska 《Studia Geophysica et Geodaetica》1994,38(1):82-92

Summary Direct measurements of the thermal plasma parameters in the topside ionosphere reveal variations of the plasmasphere boundary in the dusk sector. The ACTIVE satellite's near-polar orbits at altitudes of 500 – 1800 km around winter solstice 1989 were used to study the bulge region of the plasmasphere during intervals with different levels of geomagnetic agitation. The narrow, sharply defined trough in electron concentration corresponding to the plasmapause under quiet conditions situated at L = 6 – 7 moved to lower L-values with increasing geomagnetic activity. This narrow trough can be found in all main ion constituents. During periods of moderate geomagnetic activity, following the onset of a weak magnetic storm, a portion of the plasmaspheric bulge region was separated from the main plasmaspheric body. This can be seen in the outer ionosphere as an inner narrow trough at lower L-value. Troughs in light ions need no longer coincide with this in electron concentration. He⁺ is the most sensitive constituent reflecting the dusk sector plasmaspheric situation at this altitude.Dedicated to the Memory of Professor Karel P  相似文献   

A quantitative model of coherent,stimulated emission in astrophysical jets     

J. C. Wang  G. Z. Xie  J. Lin 《Astrophysics and Space Science》1994,213(2):257-271

On the basis of issues raised by observations of BL Lac objects and the qualitative jet model proposed by Bakeret al. in 1988, we have been led to consider the quantitative role of coherent, stimulated emission in jets and construct a new jet model of blazars in which a relativistic electron beam with an axial symmetric, power-law distribution is injected from the central engine into the jet plasma. We study quantitatively the synchrotron emission of the relativistic electron beams. Using the weak turbulent theory of plasma, we discuss the interaction between relativistic electron beams and jet plasma, and the roles of stimulated emission. The main results are:

1. The synchrotron emission increases sensitively with the increase of the angle between the direction of the beam and the magnetic field. When the direction of the beam is vertical to the magnetic field, the synchrotron emission reaches its maximum, i.e. the emitted waves are beamed in the direction of the jet axis. We suggest that radio selected BL Lac objects belong to this extreme classification.
2. The synchrotron emission of the relativistic beam increases rapidly with the increase of the Lorentz factor of the relativistic electron,γ, whenγ ≤ 22.5, then decreases rapidly with increase ofγ.
3. The stimulated emission also increases with increasing Lorentz factorγ of the relativistic electrons whenγ ≤ 35 and then decreases with the increasingγ. The maximum stimulated emission and the maximum synchrotron emission occur at different frequencies. Stimulated emission is probably very important and reasonable flare mechanism in blazars.
4. The rapid polarization position angle (PA) swings may arise from the interaction between the relativistic electron beam and the turbulent plasma.

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Densities of Huanghe River estuary and Bohai Bay waters     

陈国华  季荣  谢式南  张力军 《中国海洋湖沼学报》1994,12(2):130-135

The densities of 36 water samples from the Huanghe River estuary and Bohai Bay were determinedby a magnetic float densimcter under three temperatures from 15℃ to 25℃.All the measured densities ofsamples were greater than that of the values calculated from the International Equation of State of Seawater.The differences between the measured and calculated densities increased with the decrease of salinities.The dif-ferences appeared exponentially correlated with[Ca~(2+)]/s,[Mg~(2+)]/s and[SO_4~(2-)]/s,and had"s"type curverelationship with the alkalinity in all salinity range.But in the salinity ranging from 25.72 to 31.57,therelationships were all linear.The density difference can be estimated from the equation △ρ（10~3kg·m~(-3)）=（-2.79+236.5([Ca~(2+)]/s)/(-9.7464×10~（-3）+[Ca~(2+)]/s).It was the high alkalinity and[Ca~(2+)]/s that resulted in the measured densi-ties of seawaters being higher than the calculated densities in the Huanghe estuary and Bohai Bay.  相似文献   

Magnetic properties,self-reversal remanence and thermal alteration products of smythite     

Miroslav Krs  František Novák  Marta Krsová  Petr Pruner  Jiří Jansa 《Studia Geophysica et Geodaetica》1993,37(4):382-400

Summary This study is a follow up of the investigation of some magnetic properties and metastability of greigite in samples obtained from Miocene claystones in the Kruné hory (Erzgebirge) Piedmont basins (Bohemia). Three different methods of upgrading the smythite were applied; the magnetic properties of the concentrates are compared. The thermal conversion of smythite sets in at 200°C while greigite converts at 250°C. The first intermediate products to be formed are iron sulphides, marcasite clearly dominating over pyrite and pyrrhotite. Apart from a Fe³⁺ sulphate with a composition of Fe₂(SO₄)₃, oxidation of these sulphides gives rise to -Fe₂O₃. The result of the subsequent decomposition of the mentioned sulphate is the formation of -Fe₂O₃, which retains the sulphate structure. The final product of the thermal decomposition at 800°C is -Fe₂O₃. In the smythite concentrate the conversion to Fe³⁺ sulphate and -Fe₂O₃ is about twice as intensive as in greigite. No direct conversion to -Fe₂O₃ was found. During the thermal process self-reversals of remanence were observed, in various samples as many as four reversals in the temperature interval from 340 to 590°C. The occurrences of self-reversals of remanence were only observed at high degrees of thermal demagnetization, of the order of 10^–2 down to 10^–3 in the temperature interval of sulphide origin (below 400°C), and of the order of 10^–4 down to 10^–6 in the temperature interval of Fe-oxides origin (above 400°C).Presented at the 3rd Conference on New Trends in Geomagnetism, Castle of Smolenice, Czechoslovakia, June 22–29, 1992  相似文献   

近海核电厂核素地下水释放通量的模型计算方法     

朱君  李婷  陈超  谢添  张艾明 《吉林大学学报(地球科学版)》2021,51(1):201-211

为了定量计算陵区近海核电站排水管线泄漏情景下核素通过地下水途径向海洋环境的释放通量，以某近海核电站为例进行研究。首先，应用GOCAD软件建立三维地形地质模型，刻画地层的分布、剥蚀以及倾向等特点；然后，运用地下水数值模拟软件FEFLOW精细刻画丘陵区地下水系统的补给、径流和排泄特征；最后，以不被吸附滞留的核素³H和被吸附滞留的核素⁹⁰Sr、¹³⁷Cs为对象，通过实验测定了⁹⁰Sr、¹³⁷Cs在不同岩土介质中的分配系数，模拟计算了排水管线连续渗漏60 a后³H、⁹⁰Sr、¹³⁷Cs在地下水中的放射性分布及释放。结果表明：³H迁移速度基本与地下水流速一致，地下水中的最大放射性浓度为0.285 0 Bq/L，第20 000天时向收纳水域的释放通量达到最大值，约526 Bq/d；⁹⁰Sr吸附性能相对较弱，最大迁移距离约80 m，地下水中的最大放射性浓度为0.032 1 Bq/L；¹³⁷Cs吸附能力较强，相当长的时间内被滞留在管线附近，地下水中最大放射性浓度分别为6.840×10^-3 Bq/L，释放通量为0 Bq/d。由弥散度的不确定分析可知，弥散度越大，地下水中³H的最大放射性浓度越小，向海洋环境的释放通量越多。  相似文献   

The effect of an optically thin region on stability of an accretion disk around a supermassive black hole     

B. F. Liu  G. Z. Xie  K. F. Ji 《Astrophysics and Space Science》1995,225(2):299-314

We analyse conditions of the innermost portion of an accretion disk and establish a set of equations for this region. A stable innermost region may exist, which can probably explain the observed UV and X-ray spectra, avoiding the unstable emission. We then discuss the detailed radial structure of a disk around a black hole for typical AGN parameters and obtain different kinds of- relationships for different regions of a disk. On the basis of this, we discuss the stability. A new type of cycle is present, which we call a double S shaped cycle. In this cycle, the extent of accretion rate variability is much larger than that in dwarf nova cycles. This probably solves the problem of violent variability of AGN. In the meantime, the very high accretion rate at the hottest state in limit cycles in the unstable region may provide continuous injection of matter to the jet and power the relativistic motion of the jet.  相似文献   

Fitting matrix-valued variogram models by simultaneous diagonalization (Part I: Theory)     

Tailiang Xie  Donald E. Myers 《Mathematical Geosciences》1995,27(7):867-875

Suppose that ¯(x₁),...,¯Z(x_n). are observations of vector-valued random function ¯(x). In the isotropic situation, the sample variogram γ^*(h) for a given lag h is $$\bar \gamma ^ * (h) = \frac{1}{{2N(h)}}\mathop \sum \limits_{s(h)} (\overline Z (x_1 ) - \overline Z (x_1 )) \overline {(Z} (x_1 ) - \overline Z (x_1 ))^T $$ where s(h) is a set of paired points with distance h and N(h) is the number of pairs in s(h).. For a selection of lags h₁, h₂, .... h_k such that N (h₁) > O. we obtain a ktuple of (semi) positive definite matrices $\bar \gamma ^ * (h_{ 1} ),. . . ., \bar \gamma ^ * (h_{ k} )$ . We want to determine an orthonormal matrix B which simultaneously diagonalizes the $\bar \gamma ^ * (h_{ 1} ),. . . ., \bar \gamma ^ * (h_{ k} )$ or nearly diagonalizes them in the sense that the sum of squares of offdiagonal elements is small compared to the sum of squares of diagonal elements. If such a B exists, we linearly transform $\overline Z (x)$ by $\overline Y (x) = B\overline Z (x)$ . Then, the resulting vector function $\overline Y (x)$ has less spatial correlation among its components than $\overline Z (x)$ does. The components of $\overline Y (x)$ with little contribution to the variogram structure may be dropped, and small crossvariograms fitted by straightlines. Variogram models obtained by this scheme preserve the negative definiteness property of variograms (in the matrix-valued function sense). A simplified analysis and computation in cokriging can be carried out. The principles of this scheme arc presented in this paper.  相似文献   

Diploptene: an indicator of terrigenous organic carbon in Washington coastal sediments   总被引：1，自引：0，他引：1  

Prahl FG  Hayes JM  Xie T-M 《Limnology and oceanography》1992,37(6):1290-1300

The pentacyclic triterpene 17 beta(H),21 beta(H)-hop-22(29)-ene (diploptene) occurs in sediments throughout the Columbia River drainage basin and off the southern coast of Washington state in concentrations comparable to long-chain plantwax n-alkanes. The same relationship is evident for diploptene and long-chain n-alkanes in soils from the Willamette Valley. Microorganisms indigenous to soils and soil erosion are indicated as the biological source and physical process, respectively, for diploptene in coastal sediments. Similarity between the stable carbon isotopic composition (delta 13CPDB) of diploptene isolated from soil in the Willamette Valley (-31.2 +/- 0.3%) and from sediments deposited throughout the Washington coastal environment (-31.2 +/- 0.5%) supports this argument. Values of delta for diploptene in river sediments are variable and 8-17% lighter, indicating that an additional biological source such as methane-oxidizing bacteria makes a significant contribution to the diploptene record in river sediments. Selective biodegradation resulting from a difference in the physicochemical association within eroded particles can explain the absence of the more-13C-depleted form of diploptene in Washington coastal sediments, but this mechanism remains unproven.  相似文献   

毫秒时间尺度太阳微波辐射新特征     

金声震  李小聪  王淑兰  姬慧荣  阎元宜  赵冰 《中国天文和天体物理学报》1991,(4)

自1990年6月北京天文台太阳射电偏振仪投入实测以来,观测到一百多个“Spike”和短时标精细结构微波幅射,其中包括一些新的微波幅射特征。本文给出了主要的四点特征:(1)窄带辐射;(2)快速偏振逆转;(3)快速频率漂移;(4)不同时标的准周期振荡。  相似文献   

A Stucture—mineralogical Study of Ringwoodite     

傅平秋  谢鸿森等 《中国地球化学学报》1990,9(2):99-104

The powder XRD analysis of ringwoodite(γ-Fe2SiO4),which was synthesized in a II-stage anvil high-pressure capsule,was made,Its unit-cell parameter was calculated:a=8.219A,After the refinements,for several cycles,of the oxygen parameter x and the occupancy rate of Si in octahedron site,i.e.,the iversion degree u,the final result is R=0.077,when x=0.379A and u=27.5%,with the structural formula (Fe1.725 Si0.275)VI(Si0.725Fe0.275)IV O4 and atomic distances(Fe,Si)VI-O=2.022 A and (Si,Fe)IV-O=1.836A,Meanwhile,the Moessbauer spectroscopic analysis of the sample was conducted and the results obtained are in good agreement with those of X-ray structural analysis ,This paper focuses on the phase transformation and the properties of bonds of α－Fe2SiO4→γ-Fe2SiO4.  相似文献