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Nonlinear interactions between gravity waves and background winds

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Progress in Natural Science:Materials International 2007年第6期17卷 639-644页

作者： Liu Xiao1,2 and Xu Jiyao1(1. state key Laboratory for space weather, Center for space Science and Applied Research, chinese academy of sciences, beijing 100080, china 2. Graduate University of chinese academy of sciences, beijing 100039, china) [a]state key Laboratory for space weather Center for Space Science and Applied Research Chinese Academy of Sciences Beijing China [b]Graduate University of chinese academy of sciences Beijing China

Using the nonlinear propagating gravity waves (GW) model in the two-dimensional compressible atmosphere and the linear GW theory, the process of GW propagation in different background winds, e.g. the direction of the background wind is opposite to (dead wind) or the same as (tail wind) the direction of the horizontal phase velocity of GW, is studied. The results show that the dead wind prolongs the vertical wavelength and accelerates GW propagation. Therefore, GW propagates up to a higher height becomes instable in a short time and eventually induces an inverse jet flow. Then, the vertical wavelength is becoming short due to the nonlinear interactions between GW and the inverse jet flow. The vertical wavelength and group velocity decrease after GW propagates into the tail wind. The initial instable time is delayed. Although most of GW is trapped in the instable region, some of GW propagates above the instable region. Compared with GW propagation in the tail wind, the nonlinear interactions between GW and the dead wind are also strong. In contrast, the linear GW theory predicts that GW can propagate freely in the dead wind. The vertical wavelength simulated by the nonlinear numerical model is different from that predicted by the linear theory greatly after GW propagates into the dead wind.

关键词： gravity waves background winds vertical group velocity vertical wavelength nonlinear interactions.

The theoretical research of basic function method in incompressible viscous flow and its simulations in three-dimensional aneurysms

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Science china(Physics,Mechanics & Astronomy) 2009年第6期52卷 909-918页

作者： SHEN Fang1 & WU WangYi2 1 state key Laboratory for space weather, Center for space Science and Applied Research, chinese academy of sciences, beijing 100190, china 2.state key Laboratory of Turbulence and Complex Systems & Department of Mechanics and Engineering Science, Peking University, beijing 100871, china 1. state key Laboratory for space weather Center for Space Science and Applied Research Chinese Academy of Sciences Beijing 100190 China 2. state key Laboratory of Turbulence and Complex Systems & Department of Mechanics and Engineering Science Peking University Beijing 100871 China

Basic function method is developed to treat the incompressible viscous flow. Artificial compressibility coefficient, the technique of flux splitting method and the combination of central and upwind schemes are applied to construct the basic function scheme of trigonometric function type for solving three-dimensional incompressible Navier-Stokes equations numerically. To prove the method, flows in finite-length-pipe are calculated, the velocity and pressure distribution of which solved by our method quite coincide with the exact solutions of Poiseuille flow except in the areas of entrance and exit. After the method is proved elementary, the hemodynamics in two-and three-dimensional aneurysms is researched numerically by using the basic function method of trigonometric function type and unstructured grids generation technique. The distributions of velocity, pressure and shear force in steady flow of aneurysms are calculated, and the influence of the shape of the aneurysms on the hemodynamics is studied.

关键词： basic function unstructured grid aneurysm viscous incompressible flow artificial compressibility flux splitting

Interaction between electromagnetic waves and energetic particles by a realistic density model

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Science china(Technological sciences) 2010年第9期53卷 2552-2557页

作者： HE YiHua1,2,CHEN LiangXu1,XIAO FuLiang1 & YANG Chang1 1 School of Physics and Electronic sciences,Changsha University of Science and Technology,Changsha 410004,china 2.state key Laboratory of space weather,chinese academy of sciences,beijing 100190,china 1. School of Physics and Electronic sciences Changsha University of Science and Technology Changsha 410004 China2. State Key Laboratory of Space Weather Chinese Academy of Sciences Beijing 100190 China

Using a realistic density model,we present a first study on the interactions between electromagnetic waves and energetic particles in the inner *** calculations show that as the latitude λ increases,the number density ne increases,and resonant frequency range moves to lower pitch *** L-mode/electron and L-mode/proton interactions,the pitch angle diffusion dominates over the momentum *** indicates that L-mode waves are primarily responsible for pitch angle *** R-mode/electron interaction,the momentum diffusion is found to be comparable to the pitch angle diffusion,implying that R-mode waves can play an important role in both pitch angle scattering and stochastic acceleration of *** R-mode/proton interaction,diffusion coefficients locate primarily below pitch angle 60° and increase as kinetic energy increases,suggesting that R-mode waves have potential for pitch angle scattering of highly energetic (~1 MeV) protons but cannot efficiently accelerate protons.

关键词： wave-particle interaction energetic particles resonant frequency pitch angle and momentum diffusion density model

Synthetic aperture radar tomography sampling criteria and three-dimensional range migration algorithm with elevation digital spotlighting

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Science in china(Series F) 2009年第1期52卷 100-114页

作者： TAN WeiXian1,2,3?, HONG Wen1,2, WANG YanPing1,2, LIN Yun1,2,3 & WU YiRong1,2 1 state key Laboratory of Microwave Imaging Technology, beijing 100190, china 2 Institute of Electronics, chinese academy of sciences, beijing 100190, china 3 Graduate School, chinese academy of sciences, beijing 100190, china state key Laboratory of Microwave Imaging Technology Beijing 100190 China Institute of Electronics Chinese Academy of Sciences Beijing 100190 China Graduate School Chinese Academy of Sciences Beijing 100190 China

Based on the general geometric model of multi-baseline Synthetic Aperture Radar Tomography （TomoSAR）, the three-dimensional （3-D） sampling criteria, the analytic expression of the 3-D Point Spread Function （PSF） and the 3-D resolution are derived in the 3-D wavenumber domain in this paper. Considering the relationship between the observation geometry and the size of illuminated scenario, a 3-D Range Migration Algorithm with Elevation Digital Spotlighting （RMA-EDS） is proposed. With this algorithm 3-D images of the area of interest can be directly and accurately reconstructed in the 3-D space avoiding the complex operations of 3-D geometric correction. Finally, theoretical analyses and simulation results are presented to demonstrate the shift-varying property of the 3-D PSF and the spatialvarying property of the 3-D resolution and to demonstrate the validity of the 3-D RMA-EDS.

关键词： synthetic aperture radar tomography (TomoSAR) three-dimensional (3-D) SAR imaging 3-D sampling criteria 3-D resolution,3-D range migration algorithm with elevation digital spotlighting (RMA-EDS)

Dynamic evolution of outer radiation belt electrons driven by superluminous R-X mode waves

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Science china(Technological sciences) 2010年第10期53卷 2734-2738页

作者： XIAO FuLiang1,2, CHEN LiangXu1, HE YiHua1 & YANG Chang1 1 School of Physics and Electronic sciences, Changsha University of Science and Technology, Changsha 410004, china 2.state key Laboratory of space weather, chinese academy of sciences, beijing 100190, china 1. School of Physics and Electronic sciences Changsha University of Science and Technology Changsha 410004 China2. State Key Laboratory of Space Weather Chinese Academy of Sciences Beijing 100190 China

We present initial results on the temporal evolution of the phase space density (PSD) of the outer radiation belt energetic electrons driven by the superluminous R-X mode waves. We calculate diffusion rates in pitch angle and momentum assuming the standard Gaussian distributions in both wave frequency and wave normal angle at the location L=6.5. We solve a 2D momentum-pitch-angle Fokker-Planck equation using those diffusion rates as inputs. Numerical results show that R-X mode can produce significant acceleration of relativistic electrons around geostationary orbit,supporting previous findings that superluminous waves potentially contribute to dramatic variation in the outer radiation belt electron dynamics.

关键词： wave-particle interaction superluminous R-X waves phase space density evolution radiation belt electrons

Electron dynamics in collisionless magnetic reconnection with a PIC simulation

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chinese Science Bulletin 2009年第3期54卷 456-460页

作者： GUO Jun1,2 1 School of Mathematics and Physics, Qingdao University of Science and Technology, Qingdao 266042, china 2.state key Laboratory of space weather, chinese academy of sciences, beijing 100080, china School of Mathematics and Physics Qingdao University of Science and Technology Qingdao China state key Laboratory of space weather Chinese Academy of Sciences Beijing China

Two-dimensional particle-in-cell (PIC) simulation is used to investigate electron dynamics in colli- sionless magnetic reconnection, and the proton/electron mass ratio is taken to be mi /me = 256. The results show that the presence of a strong initial guide field will change the direction of the electron flow. The electron density cavities and the parallel electric field can be found in the electron inflow re- gion along the separatrix, and the electron inflow and density cavities only appear in the second and fourth quadrants. What is different from the results with a smaller mass ratio is that new structures appear in the diffusion region near the X line: (1) Narrow regions of density enhancement and density cavities can be found synchronously in this region; and (2) corresponding to the electron density changes near the X line, the strong parallel electric fields are found to occur in the first and third quadrants. These electric fields perhaps play a more important role in acceleration and heating electrons than those fields located in the density cavities.

关键词： PIC模仿磁链接导向场电子动力学

On the placement of actuators and sensors for flexible structures with closely spaced modes

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Science china(Technological sciences) 2010年第7期53卷 1973-1982页

作者： LIU XiaoXiang1,2 & HU Jun1,2 1 beijing Institute of Control Engineering, beijing 100190, china 2.state key Laboratory of Science and Technology on space Intelligent Control, beijing 100190, china 1. beijing Institute of Control Engineering Beijing 100190 China2. State Key Laboratory of Science and Technology on Space Intelligent Control Beijing 100190 China

This paper analyzed the fundamental limitations of previous work and developed a new method to optimally locate actuators and sensors for structures with close modes. Optimization criteria were defined based on the distinguishing modal controllability and observability measures of close modes. An appropriate genetic algorism was adopted as the optimization algorism. Solving the high order Lyapunov functions was avoided by means of the closed-form expressions for controllability and observability Grammians. Since structure with widely separated natural frequencies is approximately balanced, computational efficiency was improved by grouping close modes together and dealing with the resulting subsystems independently. Finally, the effectiveness and optimality of the novel placement scheme were verified on a model structure with close modes.

关键词： close modes controllability/observability sensor/actuator optimization criterion optimization algorithm

The developmental trend of labrum and median eyes of Orsten-type preserved Phosphatocopina (Crustacea)

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Science china Earth sciences 2010年第1期53卷 18-26页

作者： LIU Zheng 1,2 & DONG XiPing 1,2 1 School of Earth and space sciences,Peking University,beijing 100871,china 2.state key Laboratory of Palaeobiology and Stratigraphy,Nanjing Institute of Geology and Palaeontology,chinese academy of sciences,Nanjing 210008,china 1. School of Earth and space sciences Peking University Beijing 100871 China2. State Key Laboratory of Palaeobiology and Stratigraphy Nanjing Institute of Geology and Palaeontology Chinese Academy of Sciences Nanjing 210008 China

The Phosphatocopina (Crustacea,Arthropoda) is an important group of 'Orsten-type' preserved *** is resolved as the sister-group of *** we study the labrum,the median eyes,and the inner lamella of Phosphatocopina based on the selected specimens respectively from western Hunan,South china,and *** labrum characters of different species exhibit interspecific *** ratio of labrum length/shield length is significant to the reconstruction of the ontogeny of *** labrum characters should be introduced to the diagnosis of *** the earliest growth stage,the median eyes were inconspicuous,almost as flat as the other area of the ***,with the growth of the individuals they became *** were two obviously concave structures on the ventral side of the hypostome in later stages,which were the positions where the median eyes should have been *** addition,the two modes of preservation of the inner lamella,i.e.,that of shrinking and that of bulging up,are interpreted as the preservational artifact herein.

关键词： Phosphatocopina Crustacea Orsten-type preservation morphology ontogeny Cambrian South china Sweden

Prediction method for October 2003 solar storm

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Science china(Technological sciences) 2006年第5期49卷 629-640页

作者： XIE Yanqiong1, 2, 3, WEI Fengsi1, FENG Xueshang1 & ZHONG Dingkun1, 2 1. state key Laboratory of space weather, Center for space Science and Applied Research, chinese academy of sciences, beijing 100080, china 2. Graduate School, chinese academy of sciences, beijing 100039, china 3. Institute of Meteorology, PLA University of Science and Technology, Nanjing 211101, china state key Laboratory of space weather Center for Space Science Applied Research Chinese Academy of Sciences Beijing 100080 China Graduate School Chinese Academy of Sciences Beijing 100039 China Institute of Meteorology PLA University of Science Technology Nanjing 211101 China

Aiming at two intense shock events on October 28 and 29, 2003, this paper presents a two-step method, which combines synoptic analysis of space weather ——“observing” and quantitative prediction ——“palpating”, and then uses it to test predictions. In the first step of “observing”, on the basis of observations of the solar source surface magnetic field, interplanetary scintillation (IPS) and ACE spacecraft, we find that the propagation of the shocks is asymmetric relative to the normal direction of their solar sources, and the Earth is located near the direction of the fastest speed and the greatest energy of the shocks. As the two fast ejection shock events, the fast explosion of coronal mass of the extremely high temperature, the strong magnetic field, and the high speed background solar wind are also helpful to their rapid propagation. In the second step of “palpating”, we adopt a new membership function of the fast shock events for the ISF method. The predicted results show that for the onset time of the geomagnetic disturbance, the relative errors between the observational and the predicted results are 1.8% and 6.7%; and for the magnetic disturbance magnitude, the relative errors are 4.1% and 3.1%, re- spectively. Furthermore, the comparison among the predicted results of our two-step method with those of five other prevailing methods shows that the two-step method is advantageous. The results tell us that understanding the physical features of shock propagation thoroughly is of great importance in improving the prediction precision.

关键词： solar storm, interplanetary shock, interplanetary scintillation, two-step method, ISF method.