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Magnetic Energy of Force-Free Fields with Detached Field Lines

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Chinese Journal of Astronomy and Astrophysics 2003年第6期3卷 555-562页

作者： Guo-Qiang Li and You-Qiu HuSchool of earth and space sciences,{3., hefei 2.002. School of earth and space sciences University of Science and Technology of China Hefei 230026

Using an axisymmetrical ideal MHD model in spherical coordinates, we present a numerical study of magnetic configurations characterized by a levitating flux rope embedded in a bipolar background field whose normal field at the solar surface is the same or very close to that of a central dipole. The characteristic plasma β (the ratio between gas pressure and magnetic pressure) is taken to be so small (β = 10-4) that the magnetic field is close to being force-free. The system as a whole is then let evolve quasi-statically with a slow increase of either the annular magnetic flux or the axial magnetic flux of the rope, and the total magnetic energy of the system grows accordingly. It is found that there exists an energy threshold: the flux rope sticks to the solar surface in equilibrium if the magnetic energy of the system is below the threshold, whereas it loses equilibrium if the threshold is exceeded. The energy threshold is found to be larger than that of the corresponding fully-open magnetic field by a factor of nearly 1.08 irrespective as to whether the background field is completely closed or partly open, or whether the magnetic energy is enhanced by an increase of annular or axial flux of the rope. This gives an example showing that a force-free magnetic field may have an energy larger than the corresponding open field energy if part of the field lines is allowed to be detached from the solar surface. The implication of such a conclusion in coronal mass ejections is briefly discussed and some comments are made on the maximum energy of force-free magnetic fields.

关键词： Sun: magnetic fields - Sun: coronal mass ejections (CMEs) -methods: numerical

Re-Os isotopic system and formation age of subcontinental lithosphere mantle

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Chinese science Bulletin 2000年第3期45卷 193-200页

作者： ZHI Xiachendepartment of earth and space {3.s, university of science and technology of china, hefei 2.002., china Advance Research Center for earth {3. and Astronomy, USTC, Third World Academy of {3., hefei 2.002., china Laboratory of Chemical Geodynamics, USTC, hefei 2.002., china department of earth and space {3.s University of Science and Technology of China Hefei China Advance Research Center for earth science and Astronomy USTC Third World Academy of Science Hefei China Laboratory of Chemical Geodynamics USTC Hefei China

The determination of the formation age of subcontinental Lithosphere Mantle (SCLM) is a widely concerned issue in mantle geochemistry. it is difficult to obtain the formation age of SCLM using lithophile isotopic systems such as Rb-Sr, Sm-Nd, U-Th-Pb, ete., but as siderophile elements, the Re-Os isotopic system provides a powerful tool for that work. Here a comprehensive review on the recent development in Re-Os dating for SCLM has been given.

关键词： Re-Os isotopic dating subcontinental lithospheric mantle mantle derived peridotites Re depleted model age whole rock isochronological age.

Characteristics of low-frequency oscillation intensity of airsea turbulent heat fluxes over the northwest Pacific

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science china earth sciences 2009年第8期52卷 1137-1151页

作者： LI Gen, REN BaoHua, ZHENG JianQiu & WANG Jun School of earth and space sciences,{3., hefei 2.002., china 1. School of earth and space sciences University of Science and Technology of China Hefei 230026 China

Based on the daily turbulent heat fluxes and related meteorological variables datasets (1985-2006) from Objectively Analyzed air-sea Fluxes (OAFlux) Project of Woods Hole Oceanographic Institution (WHOI), characteristics of low-frequency oscillation intensity of air-sea turbulent heat fluxes over the northwest Pacific are analyzed by linear perturbation method and correlation analysis. It can be concluded that: 1) the distribution of low-frequency oscillation intensity of latent heat flux (LHF) over the northwest Pacific is mainly affected by that of low-frequency oscillation intensity of anomalous air-sea humidity gradient (Δq′) as well as mean air-sea humidity gradient ( Δ q), while the distribution of low-frequency oscillation intensity of sensible heat flux (SHF) is mainly affected by that of low-frequency oscillation intensity of anomalous air-sea temperature gradient (ΔT′). 2) The low-frequency oscillation of turbulent heat fluxes over the northwest Pacific is the strongest in winter and the weakest in summer. And the seasonal transition of low-frequency oscillation intensity of LHF is jointly influenced by those of low-frequency oscillation intensity of Δq′, low-frequency oscillation intensity of anomalous wind speed (U′), Δ q and mean wind speed (U ), while the seasonal transition of low-frequency oscillation intensity of SHF is mainly influenced by those of low-frequency oscillation intensity of ΔT′ and U . 3. Over the tropical west Pacific and sea areas north of 20°N, the low-frequency oscillation of LHF (SHF) is mainly influenced by atmospheric variables qa′ (Ta′) and U′, indicating an oceanic response to overlying atmospheric forcing. In contrast, over the tropical eastern and central Pacific south of 20°N, qs′ (Ts′) also greatly influences the low-frequency oscillation of LHF (SHF).

关键词： northwest Pacific latent heat flux sensible heat flux low-frequency oscillation

Mineralogical evidence for continental deep subduction

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Chinese science Bulletin 2003年第10期48卷 952-954页

作者： ZHENG Yongfei School of earth and space sciences,{3., hefei 2.002., china School of earth and space science University of Science and Technology of China China

Discusses the findings of mineralogical investigations into the geodynamic processes of plate subduction and exhumation. Identification of the ultrahigh pressure index minerals in Dabie-Sulu metamorphic rocks; Finding... 详细信息

关键词：矿物学超高压石英地球表面正态重力梯度

Coronal Flux Rope Equilibria in Closed Magnetic Fields

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Chinese Journal of Astronomy and Astrophysics 2003年第3期3卷 241-246页

作者： Zhen Wang and You-Qiu HuSchool of earth and space sciences,{3., School of earth and space sciences University of Science and Technology of China Hefei 230026

Using a 2.5-dimensional ideal MHD model in Cartesian coordinates, weinvestigate the equilibrium properties of coronal magnetic flux ropes in background magnetic fieldsthat are completely closed. The background fields are produced by a dipole, a quadrupole, and anoctapole, respectively, located below the photosphere at the same depth. A magnetic flux rope isthen launched from below the photosphere, and its magnetic properties, i.e., the annular magneticflux Φ_p and the axial magnetic flux Φ_z, are controlled by a single emergence parameter. Thewhole system eventually evolves into equilibrium, and the resultant flux rope is characterized bythree geometrical parameters: the height of the rope axis, the half-width of the rope, and thelength of the vertical current sheet below the rope. It is found that the geometrical parametersincrease monotonically and continuously with increasing Φ_p and Φ_z: no catastrophe ***, there exists a steep segment in the profiles of the geometrical parameters versus eitherΦ_p or Φ_z, and the faster the background field decays with height, the larger both the gradientand the growth amplitude within the steep segment will be.

关键词： sun: magnetic fields sun: corona

Mantle xenoliths from Late Cretaceous basalt in eastern Shandong Province: New constraint on the timing of lithospheric thinning in eastern china

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Chinese science Bulletin 2003年第19期48卷 2139-2144页

作者： YAN Jun, CHEN Jiangfeng, XIE Zhi & ZHOU Taixi School of earth and space sciences,{3., hefei 2.002., china Yarmouk university Irbid - Jordan School of earth and space sciences University of Science and Technology of China Hefei 230026 China

The age of the alkali basalt from Daxizhuang in Jiaozhou, eastern Shandong, was determined to be 73.5±0.3.Ma by 40Ar-3.Ar technique. The basalt gave high eNd(t) values of +7.5 and +7.6, suggesting that the primitive magma was derived from depleted asthenospheric mantle with a formation depth of about 65—95 km. Spinel-lherzolite xenoliths have been discovered in the basalt. The Fo values of olivine from the xenoliths range from 88 to 89. The estimated equilibrium P-T conditions of spinel-lherzolite xenoliths are about 2.0 GPa and 1010—1140℃, suggesting an equilibrium depth of about 65 km. Geochemical characteristics of the Late Mesozoic (125—115 Ma) mantle-derived rocks in Shandong Province suggest an enriched lithospheric mantle along the southern margin of the North china block. However, geochemical characteristics of the Late Cretaceous basalts in Daxizhuang and the equilibrium P-T condition estimated from the xenoliths suggest that the lithosphere at 73.Ma ago was as thick as that of the Cenozoic in the region. Additionally, the xenoliths are rich in basaltic-component, suggesting a derivation from a newly-formed lithosphere. Therefor, lithospheric thinning took place at a time interval between about 120 and 73.Ma along the southern margin of the North china block.

关键词：覆盖捕虏岩白垩纪玄武岩山东东部地区岩石圈稀释化 ^40Ar-^3.Ar技术

THE OPTIMAL MOTION OF TWO-DIMENSIONAL UNDULATING PLATE SWIMMING IN FLUID FLOW

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Journal of Hydrodynamics 2011年第1期23卷 12-20页

作者： QIAN Qin-jian LIU Miao-qin SUN Liang SUN De-jun department of Modern Mechanics University of Science and Technology of China Hefei 230026 China School of earth sciences University of Science and Technology of China Hefei 230026 China

The optimum shape of a two-dimensional undulatory plate in its motion in fluid flow is analyzed and the physical parameters（the thrust and the power）are calculated by the boundary element *** the commonly used Lagrange multiplier method,only a saddle point of the optimum solution can be obtained,but not the solution itself due to the singularity of the *** eliminate the singularity,a method is proposed by adding an amplitude *** new method is a generalization of that proposed by Wu,and it can be applied to more complex *** optimum shape of the linearly varying amplitude motion is studied in *** is shown that both the maximum and the minimum solutions exist when the frequency is higher than a critical *** a high frequency,the maximum efficient motion with a large amplitude at the leading edge and a small amplitude at the trailing edge induces a large leading edge suction *** the frequency decreases,the leading edge suction force decreases to a minimum and then *** high wavenumbers,there exists an optimum frequency with the maximum *** efficiency holds over a large range of *** optimum efficiency increases as the wavenumber *** increase of the wavenumber can also reduce the leading edge suction *** optimization method can also be applied to a quadratically varying amplitude *** is found that the optimum efficiency is larger than that for the linearly varying amplitude ***,the additional efficiency is relatively small,especially as the original efficiency is already high enough.

关键词： two-dimensional undulating plate boundary element method optimization

TOPOLOGICAL CONFIGURATIONS OF POSSIBLE REAL NETS IN BINARY n+m(m≥3. PHASE MULTISYSTEMS

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science in china,Ser.B 1986年第10期29卷 1096-1109页

作者：程伟基 department of earth and space {3.s university of science and technology of{3. hefei

This paper further summarizes the method and results developed to find all possible real nets in binary n+3.phase multisystems, and emphasizes that there is a definite relationship between configurations and symbols of stable and metastable invariant points of nets or positions of phases as symbols on the chemographic bar. On the basis of these, a general principle is developed to construct and check possible neets in binary n+m (m>3. phase multisysterns: this sort of nets must be the reasonable combination of one or more than one distinct binary n+3.phase multisystem subnets, in which the number of points missing respectively same m—3.phases in n+3. Therefore, the binary n-4-3.phase nets are basic construction units of the binary n+m(m>3. phase nets. As an instance, the maximum partially closed net in binary n+4 phase multisystems, which has the most stable invariant points, is constructed, and it is indicated that this sort of net is unique.

关键词： PHASE MULTISYSTEMS TOPOLOGICAL CONFIGURATIONS OF POSSIBLE REAL NETS IN BINARY n+m net NETS

Decoupling of surface and subsurface sutures in the Dabie orogen and a continent-collisional lithospheric-wedging model: Sr-Nd-Pb isotopic evidences of Mesozoic igneous rocks in eastern china

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Chinese science Bulletin 2003年第8期48卷 831-838页

作者： LI Shuguang & YANG Wei School of earth and space sciences, {3. of science and Tech-nology of china, hefei 2.002., china School of earth and space sciences University of Science and Technology of China

There are significant differences of Nd and Pbisotopic compositions between Mesozoic mafic igneous rocks from the North china Block (NCB) and the South chinaBlock (SCB). Mesozoic mantle-derived igneous rocks fromthe North china Block have very low e Nd values (-15 to -21), and 206Pb/204Pb ratios ( -10 and 206Pb/204Pb > 18.3. The verylow e Nd values (-16 to -20) and 206Pb/204Pb ratios (3. of the early Cretaceous mafic-ultramafic intrusions developedin the north part of the Dabie orogen (NDZ) suggest that the deep lithosphere underneath the NDZ belongs to the NCBbut not the SCB. Therefore, although the surface suture be-tween the NCB and SCB is located on the north side of theNDZ, the subsurface suture between the NCB and SCBshould be located to the south side of the NDZ. This is con-sistent with the previous suggestion that the subsurface su-ture in the Sulu terrane east of the Tanlu fault was the south displacement, but contradictory to northward continentalsubduction of the SCB. A continent-collisional lithospheric-wedging model can interpret the decoupling of the surface and subsurface sutures in the Dabie-Sulu orogen. After slabbreak-off, the continuing convergence of two continental blocks must increase the compression force acting on the suture zone, which might induce the lithosphere splitting of SCB. Thus, the lower crust and lithospheric mantle on thesouth margin of the NCB can wedge into the north margin of the lithosphere of the SCB along the Dabie-Sulu collisionzone. This process caused the overthrust of the mid-upper continental crust with exhumed ultrahigh pressure meta-morphic (UHPM) rocks and underthrust of the deep litho-sphere of the SCB. It could be an important mechanism re-sponsible for the second rapid cooling and uplifting of theUHPM rocks and lithospheric delamination as well as thecorresponding magmatism in Jurassic in the Dabie *** southward movement of subsurface suture

关键词：大别造山带同位素中生代火成岩中国