Table of Content

    15 November 2006, Volume 26 Issue 6 Previous Issue    Next Issue
    Influence of a Streamer Background With Nested Close Magnetic Structures on the Properties of CME Initiated From Its Bottom
    YE Zhanyin;WEI Fengsi;WANG Chi;FENG Xueshang;ZHONG Dingkun
    2006, 26 (6):  409-414.  doi: 10.11728/cjss2006.06.409
    Abstract ( 2014 )   PDF (2854KB) ( 1254 )   Save
    The influence of a streamer background with nested close magnetic structures on the properties of CME initiated from its bottom is investigated in a solar meridian plane. In the streamer there contain three small-scale close magnetic field structures with the magnetic direction of the middle one opposite to that of the solar global dipole. A CME triggering model made up of cocircular magnetic field lines is taken to emerge from the solar equator at the inner boundary, where the middle small-scale close magnetic field structure locates, of the computational domain. The magnetic field direction in the front half of the CME triggering model with a radius a = OARs (Rs is solar radius) is opposite to that of the magnetic field line at its emerging position and same to that of the streamer global dipole. It is found from numerical simulation that: the CME triggering model, with a ratio of plasma pressure at its center and that at its edge m ≥ 2, can trigger a CME and can not when m 〈 2. The error for this numerical conclusion is less than 1%.
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    Correlation Height of the Emission Source of Si Ⅱ in a Coronal Hole Region
    ZHOU Guiqing;HE Jiansen;TU Chuanyi;E. Marsch
    2006, 26 (6):  415-420.  doi: 10.11728/cjss2006.06.415
    Abstract ( 1924 )   PDF (1194KB) ( 944 )   Save
    The height of the source for Si Ⅱ represents the altitude of the bottom of the solar transition region. It is a new method to determine the so-called correlation height, by correlating the radiance of the FUV/EUV line with the magnetic field from a force-free extrapolation, as the height of the FUV/EUV emission source. A previous study found that the height of the source for SiⅡdetermined by applying this method in a coronal hole region is higher than that in the traditional view, which is so limited that it requires more data analysis to check. Using this method, the radiance data of SiⅡ, obtained in a south coronal hole region of the Sun by SOHO/SUMER, and the photospheric magnetic field, measured by NSO/KP (National Solar Observatory/Kitt Peak), were analyzed. And the correlation height of SiⅡ is determined to be about 5.0 Mm for the data sets selected from a south coronal hole region. This result supports the recent conclusion that the bottom of the transition region in the coronal hole region is quite higher than that in the quiet-Sun region. Besides, a little difference from the previous study is found and the reason for this is speculated.
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    Study on the Relationship Between Interplanetary Disturbances and Magnetic Storms With Different Intensities
    ZHAO Mingxian;LE Guiming;LIU Yujie
    2006, 26 (6):  421-426.  doi: 10.11728/cjss2006.06.421
    Abstract ( 1775 )   PDF (677KB) ( 1123 )   Save
    The solar wind data observed by ACE satellite during 1997--2004 and the corresponding Dst indices are used to analyze the correlations of the interplanetary parameters (Bz,Ey,v,Pk,|B|,ε'=vxB2zsin4(θ/2)) with the Dst indices, focusing on the magnetic storms of different intensities. The results show that Ey and Bzcorrelate well with Dst index. It is found that the larger the storm intensity is, the better the correlative relationship between interplanetary parameters and Dst indices is. As for moderate storms (-100nT〈 Dstmin≤ -50nT), there is a low correlative relationship between interplanetary parameters and Dst indices. When dividing storms into two levels, that is -150 nT〈 Dstmin ≤ -50 nT and Dstmin ≤ -150 nT, there is a best correlative relationship between cr and Dst. As a single factor, Ey correlate best with Dst, and the inferior one is Bz.
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    Investigating the Geometrical Structure of Magnetic Field Lines in the Magnetosphere
    QU Shaojie;SHEN Chao;LIU Zhenxing;TIAN Baoning
    2006, 26 (6):  427-431.  doi: 10.11728/cjss2006.06.427
    Abstract ( 1919 )   PDF (1700KB) ( 1247 )   Save
    The geometrical structure of magnetic field in the magnetosphere is an important issue for discussion in space physics. In this paper an analysis has been made to some regions of magnetosphere, including the Nightside, Cusp and Duskside. By applying the Curvature Radius Method to the magnetic field data measured by four satellites of Cluster, the geometrical structure of Magnetic Field Lines, including the curvature radius, directions of curvature and normal of the osculating planes of the Magnetic Field Lines have been investigated. Then the spacial configuration of Magnetic Field Lines is known ,and consequently the three dimensional structures of the corresponding regions are achieved according to the anterior results. And finally the results testified the validity of the Curvature Radius Method. If more detailed datas are supplied, a three-dimentional model of the whole magnetosphere can be built by extending the method to the other regions in magnetosphere. So the significance of the research is very clear for space science.
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    Collisionless Magnetic Reconnection in Presence of a Guide Field
    FU Xiangrong;GUO Jun;WANG Shui
    2006, 26 (6):  432-439.  doi: 10.11728/cjss2006.06.432
    Abstract ( 2249 )   PDF (3137KB) ( 1237 )   Save
    This paper studies the coUisionless magnetic reconnection in the presence of different guide fields using two-and-a-half dimensional full particle simulation. The results show that, a strong guide field with Bz0 〉 0.5B0 will not only strongly alter the motion of electrons but also change the structure of electric field and velocity field around the reconnection region, thus affect the reconnection rate and electron accelerating process. General Ohm's law for two-fluid MHD model is employed to explain the characteristics of these electric field structures. And by tracing beams of electrons near the diffusion region, it is found that in the 2D model, electric field component perpendicular to the simulation plane and located at the center of diffusion region plays the major role in the electron acceleration, while the other two components contribute very little, no matter the guild field is strong or not.
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    Analysis of Global Ionospheric TEC Disturbance During the Magnetic Storm in Nov. 2004
    LI Qiang;ZHANG Donghe;QIN Jiansheng;XIE Shibiao;ZHAO Yingxin;YE Jinfeng;MO Xiaohua;XIAO Zuo
    2006, 26 (6):  440-444.  doi: 10.11728/cjss2006.06.440
    Abstract ( 2469 )   PDF (1330KB) ( 1119 )   Save
    The characteristics and development of the ionospheric storm between Nov. 6 and Nov. 12, 2004 was studied using the total electron content (TEC) derived from GPS data observed by globally-distributed GPS stations under International GPS Service for Geodynamics (IGS). It was found that when magnetic storm was in its main phase on Nov. 8, the ionospheric positive storm occurred over a large region of mid-and low latitude in the day time. And during the recovery phase on Nov. 10, when Dst index reached its minimum, the global ionosphere was intensely disturbed and both positive and negative effects appeared. During this storm, negative effects appeared more intensely in the southern hemisphere (the summer hemisphere) than in the northern one, which is consistent with previous statistic results that negative storms have a proneness to appear in the summer hemisphere. It has been also observed that during the storm the value of night time TEC is low comparing the night TEC with no storm period, for which many mechanisms has been proposed. Because of the complex evolution process of ionospheric storm, more data including from other observation methods during other large ionospheric storms needs to be collected and analyzed.
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    Availability Study of Estimating Total Ozone by Scattered Ultraviolet From the Clear Zenith Blue Sky
    JIANG Fang;WANG Yingjian;WANG Yongmei;ZHANG Xiaoqing
    2006, 26 (6):  445-451.  doi: 10.11728/cjss2006.06.445
    Abstract ( 2135 )   PDF (2889KB) ( 1044 )   Save
    Within the limitation of SBTART model, the paper is concerned with the preliminary study of the feasibility of determining total atmospheric ozone by scattered ultraviolet radiation from the clear zenith blue sky. The calculation results indicate that the larger sΩ0 value is, the longer the wavelength used for deriving total ozone should be. In addition, Lower total ozone content value in the atmosphere would induce less accurate retrieval results than higher one. The accuracy of total ozone determination, based on measurements at a single wavelength, is not good even if the intensity is measured within aa accuracy of 1%, reflectivity within 0.05, and surface pressure within 50 hPa.Measurements on a pair of wavelengths are found to reduce the effects of reflectivity and pressure and the retrieval results are in better accuracy. Similarly the shorter wavelength between the pair of wavelengths should be longer with the larger value of SJ?o. The wavelengths λ1 = 0.308 μm, λ2 ~- 0.3125 μm, λ3 -- 0.3175 μm associate with λ4 = 0.3300 μm respectively and produce three pairs denoted by pl, p2, p3 orderly, pl is selected when sΩ0 ≤ 1.5, p2 is selected when 1.5 〈 sΩ0 ≤ 3.0, p3 is selected when sΩ0 〉 3.0. Based on the selection principle the accuracy of retrieval results is 4% at least if the intensity is measured with accuracy within 1%, reflectivity within 0.05~ and surface pressure within 50 hPa.
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    Collision Probability Analysis and Application of Cataloged Space Debris
    CHENG Tao;LIU Jing;WANG Ronglan;YU Youcheng
    2006, 26 (6):  452-458.  doi: 10.11728/cjss2006.06.452
    Abstract ( 2501 )   PDF (1514KB) ( 1389 )   Save
    With the expansion of the human's activity in exploring, utilizing the outer space, protecting space environment have become the most significant task in space navigation. Since the neglect of the space debris environment in the past century, the total number of orbital space debris increases rapidly, which leads to an unacceptable large risk of collision to spacecraft. Space Debris Collision Avoidance (SDCA) is the only strategy to reduce the risk of collision, when the dimension of space debris is lager than 10 cm. The decision whether the avoiding maneuver is necessary depends on the analysis of conjunction, the rigorous calculation and assessment of collision risk between spacecraft and debris and compare to the collision criterion. This paper initially introduces the flow of the Space Debris Collision Avoidance System (SDCAS), with comparing of the two kinds of warning criterion, the main topic on method of collision probability is evoked. Collision probability is a new type of warning criterion, which not only takes the miss distance into consideration, but regards all the geometrical parameters during the approach as the factor to the collision risk, combining with all influence of these parameters. Eventually, with the detailed analysis, the effect of the covariance or uncertainty to the collision probability has been drawn to the surface, which plays an indispensable role in measuring the risk of collision. The attitude of the error ellipse which is constructed by the covariance has also affect the result of collision probability. Based on the analysis of covariance, the method of collision probability posts many advantages to the Box method. Especially, the rate of false warning has been decreased dramatically.
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    Research on System Integration Model and Strategy of Aerospace Engineering
    YANG Tianshe;XI Zheng;HUANG Yongxuan;SUN Yanhong
    2006, 26 (6):  459-464.  doi: 10.11728/cjss2006.06.459
    Abstract ( 1894 )   PDF (1240KB) ( 924 )   Save
    System Integration is one of the most important parts of System Engineering, and it determines the success or failure of a large-scale engineering project. System integration of largescale engineering project concerns time, cast, risk, and so on. Time integration is more important and difficult among them. Aerospace Engineering is a typical kind of large-scale engineering and is in general divided into many subsystems. System integration process of aerospace engineering has many steps and impossible paths, and complicated relations exist among these steps and paths. Schedule delay and performance dissatisfaction resulting from system integration occur frequently in the system integration process of aerospace engineering. In this paper, firstly, two models (GAN model and InfoGap model) and strategies (Single Stage Integration strategy and Incremental Integration strategy) of system integration are introduced briefly; then, the models establishment and strategies design of system integration of aerospace engineering are discussed; finally, the correlative problems are analyzed.
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    A New Orbit Forecast Method Based GPS for High Precision Ephemeris of Earth Resource Satellite
    YANG Jin;MA Guangbin;ZHANG Wenyi
    2006, 26 (6):  465-469.  doi: 10.11728/cjss2006.06.465
    Abstract ( 2001 )   PDF (1107KB) ( 794 )   Save
    With the development of technology, the method that acquires satellite ephemeris data from onboard GPS data directly becomes an important means of satellite orbit determination and an important research task. The satellite ephemeris obtained by GPS receiver is in an instantaneous state at a certain moment. The acquisition for continuous satellite ephemeris data needs further processing. The commonly used processing methods are based on geometry and dynamics. The calculation error of geometry would be great when the frequency of the instantaneous satellite ephemeris is low. Further more it is unable to conduct the extrapolating of the satellite orbit when only one group satellite ephemeris exists. Based on the analysis of Earth Resources Satellite orbit character, this paper proposed a novel reduced dynamic orbit determination which can reduce the calculation error of satellite ephemeris. The model breaks up satellite motion into simple harmonic motion in rectangular coordinate. The Paper make use of this determination to realize the orbit extrapolate algorithm. Finally, the result of our experiment indicates that the algorithm can reach high precision and reduce the complexity of calcLiiation process at the same time.
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    Study of the Passive Vibration Isolation System for the Space Scientific Experimental Rack
    WANG Ke;GU Yidong
    2006, 26 (6):  470-476.  doi: 10.11728/cjss2006.06.470
    Abstract ( 1967 )   PDF (3857KB) ( 1014 )   Save
    The second phase of the manned space flight project will develop manned space labs for a series of space scientific experiments. Vibration isolation system is indispensable for both International Space Station and Shenzhou spaceship to satisfy the requirement of scientific experiments. In this paper, the passive vibration isolation system for the space scientific experimental rack in manned space shuttle has been studied and designed. According to the actual mounting, the vibration isolation system layout is designed. As a rigid body, a 6-degree of freedom dynamic model of the scientific experimental rack is developed, a 3D model of experimental rack and vibration isolation system is created in ADAMS, and system performance in time domain and frequency domain are obtained. The system parameters are optimized to improve isolation performance.
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    Single Event Simulation and Evaluation Methodology for Spaceborne Software Radio Platform
    XING Kefei;YANG Jun;WANG Yueke;PAN Huafeng;JI Jinming
    2006, 26 (6):  477-481.  doi: 10.11728/cjss2006.06.477
    Abstract ( 2439 )   PDF (1653KB) ( 1032 )   Save
    After a brief introduction of the software radio technique used in spacecrafts and satellites, an architecture of a Spaceborne Software Radio Platform (SSRP) is given. The Single Event Effects (SEEs) for the SSRP' reliability is presented and a novel method is listed for the simulation and evaluation of SSRP' reliability design technology. As the main components of the SSRP Field Programmable Gate Array (FPGA) and Digital Signal Processor's (DSP) SEEs and reliability are even important, A fault injection method is listed for the simulation of SEEs and is introduced for the evaluation of the FPGA and DSP's reliability design. The design idea and fault injection method has the advantage of cheap and flexible and it has been adopted in a spaceborne multiuser receiver based on direct sequence spread spectrum technology and proved to be effective in the environmental test. With the reliability design method, low grade with high performance device is possible to be used in space.
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    Passive Positioning Algorithm Based on Beidou Double-Star Positioning System
    QI Huan;CHEN Yingchun;XIA Shuang
    2006, 26 (6):  482-486.  doi: 10.11728/cjss2006.06.482
    Abstract ( 2036 )   PDF (3143KB) ( 1055 )   Save
    Being an active positioning system, China's Beidou Double-star Positioning System cannot achieve continuous and real-time positioning, and capacity of the system is limited as users consume system resources during positioning. In order to overcome these shortcomings, a passive positioning algorithm is proposed based on three-dimensional grid search. According to a newly defined cost function, as well as the data collected from the two synchronous satellites, atomic clock and altitude gauge carried by a user, passive positioning is fulfilled through the grid search algorithm. The operational area of Beidou system is first divided into some grids. Secondly, the grid with the lowest cost and its eight neighboring grids, i.e. sub-area, is chosen as the next search area. Thirdly, the sub-area is further divided into some sub-grids so as to calculate the cost of each sub-grid and find out the sub-grid with the lowest cost. This process repeats until the positioning accuracy is satisfactory or a predetermined iteration time is reached. At this point, the center of the current search grid is taken as the position of the user. During simulation, a digital map is used to validate the three-dimensional search algorithm. The influence of ionospheric error on positioning accurate is considered. Simulation results show that the method is fast and accurate enough for real-time positioning, and that the number of partition grids greatly affects positioning accuracy and positioning time. It is a possible way to turn the active Beidou Double-star positioning system into a passive one.
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    Calibrating Antenna Phase Center in GPS Radio Occultation Measurements
    DU Qifei;SUN Yueqiang;LIU Zhengting;TAO Peng;LI Changyuan;YU Fang
    2006, 26 (6):  487-490.  doi: 10.11728/cjss2006.06.487
    Abstract ( 1909 )   PDF (1330KB) ( 1107 )   Save
    Antenna is a main part in the CPS receiving system. Its performance has a direct effect on receiving CPS signal efficiently. The variation of antenna phase center affects the measurement of carrier phase and C/A code. The antenna phase center is not always stable. Its coordinates will change with the variation of the signal directions. To fit some high accuracy survey, the phase center variations must be taken into account. This article presents a method for calibrating CPS antenna phase center. Phase patterns are measured at different azimuth and different elevation angles in an anechoic chamber. The coordinates of the phase center can be calculated by analyzing the data from the phase patterns. The dual-band CPS antenna that designed and manufactured by us was tested. The antenna phase center variation is within 4 mm at different elevations ranged from -75° to +75°.
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