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Table of Content

    25 September 2013, Volume 33 Issue 5 Previous Issue    Next Issue
    Entropy Parameter of Jupiter’s Magnetosphere
    Lu Bin, Chen Chuxin
    2013, 33 (5):  465-472.  doi: 10.11728/cjss2013.05.465
    Abstract ( 1749 )   PDF (586KB) ( 1320 )   Save

    The nonconservation of entropy in space plasmas can result from magnetic reconfiguration as well as nonadiabatic processes such as plasma transport and energy transport. The theory of plasma transport in Earth's plasma sheet depends critically on the entropy parameter PV5/3, where P is particle pressure and V is the volume of a closed flux tube containing one unit of magnetic flux. The stability and dynamics of the magnetosphere could be indicated by the change of entropy parameter. This paper shows the distribution of entropy parameter in the Jupiter's stable magnetosphere model using the analysis method in Earth's plasma sheet. The entropy parameter increases by four order of magnitudes quickly between 5Rj and 55Rj and then decline slowly. The result shows that the magnetosphere is unstable beyond 55Rj. The paper also shows the contour of the entropy parameter after the fictitious magnetic reconnection. It points out that the reconnection near the equatorial plane is caused by the rupture and reconnection of the flux tube which transports tailward.

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    Characteristic of Lunar Water Distribution, Using Solar Wind as a Possible Source
    Chen Ting, Zhao Hua, Zhang Yiteng, Li Lei
    2013, 33 (5):  473-479.  doi: 10.11728/cjss2013.05.473
    Abstract ( 1972 )   PDF (2411KB) ( 1059 )   Save

    Recent observations confirmed that the lunar surface is hydrated. Former Monte-Carlo simulation has estimated the potential amount of water in the polar regions, whereas the distribution character of water in the lunar space environment remains unknown. By applying a combined model of Monte-Carlo method and a central force algorithm based on energy conservation, this paper has investigated the character of the water molecular density distribution in the Moon's exosphere and the evolution of global surficial density, using solar wind proton as the water origin. The results show about 4.12% of all water molecules travel down to the Permanently Shadowed Regions (PSR) and become stable, under the circumstance that the timescale for photo-dissociation is 64000 seconds for water, which agrees with the previous simulation. It also indicates there are larger abundances of water in higher latitude regions.

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    Statistical Analysis of Solar Cycle Distribution of Moderate Storms
    Zhang Yong, Le Guiming, Zhao Haofeng, Yin Zhiqiang
    2013, 33 (5):  480-485.  doi: 10.11728/cjss2013.05.480
    Abstract ( 1911 )   PDF (757KB) ( 1448 )   Save

    In this paper, the statistical analysis of solar cycle distribution of moderate geomagnetic storms (-100nT< Dst ≤-50nT) is investigated based on observed data. The results show that the yearly number of moderate storms have multi-peaks in each cycle with the highest peak appeared in the descending phase of the cycle. This means that the highest peak of moderate storms have a time lag with respect to the yearly number of sunspot numbers. The time lag is about 2~3 year. More than 70% moderate storms appeared in the descending phase of a solar cycle. During the solar maximum, there are less moderate storms occurred than that occurred in other period of a solar cycle. Monthly mean moderate storm numbers and smoothed monthly mean sunspot numbers is also investigated in this paper. The results show that the time of moderate storms peaks lag behind that of the time of sunspots peaks, the time of peaks of both moderate storms and sunspots is different, and the time differences are different in different solar cycles, ranging from a few years to just a few months.

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    Response of the Ionospheric Equivalent Current Systems to Interplanetary Shocks
    Zhang Qingmei, Sun Tianran, Zhang Jiaojiao, Li Chuanqi, Wang Chi
    2013, 33 (5):  486-493.  doi: 10.11728/cjss2013.05.486
    Abstract ( 1858 )   PDF (3073KB) ( 1581 )   Save

    Interplanetary (IP) shocks, one of the important causes of the magnetosphere ionosphere disturbances, could affect the geo-magnetic field by changing the current systems in the magnetosphere——ionosphere region. By using a global three dimensional MHD simulation code, we analyze the immediate responses of the Equivalent Current Systems (ECS) in the Earth's ionosphere to the impact of IP shocks. The model results show that after the shock arrival a pair of abnormal Field-Aligned Current (FAC) appears, flowing into and out of the ionosphere on the dusk and dawn side respectively. Also developed in the ionosphere is the two-cell ECS: an anticlockwise circulation in the dawn hemisphere and a clockwise one in the dusk hemisphere. The two ECS vortices shift poleward and tailward after their formation. In the meantime, their intensities increase at first and then decrease to virtually disappear within tens of seconds. At last the ECS pattern reaches a quasi-steady state which is controlled by the interplanetary conditions downstream of the IP shock. The quantitative characteristics of such response processes depend on the intensity of the IP shock: for a stronger shock, the two-cell ECS becomes more intense, and its lifetime is shorter.

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    Response of the Ionospheric F2-region Over Irkutsk and Hainan to Strong Geomagnetic Storms
    E B Romanova, G A Zherebtsov, K G Ratovsky, N M Polekh, J K Shi, X Wang, G J Wang
    2013, 33 (5):  494-500.  doi: 10.11728/cjss2013.05.494
    Abstract ( 1786 )   PDF (1270KB) ( 1199 )   Save

    The ionospheric responses to two strong storms on 17-19 August 2003 and 22-23 January 2004 are studied, using the data from Irkutsk (52.5°N, 104°E) and Hainan (19.5°N, 109°E) ionospheric stations. The analysis of variations in relative deviations of the critical frequency Δf0F2 revealed that at middle latitudes (Irkutsk) negative disturbances were observed in the summer ionosphere; positive and negative ones, in the winter ionosphere during the main and recovery phases respectively. At low latitudes (Hainan), the disturbances were positive in all the cases considered. Mechanisms of the disturbances were analyzed with the aid of empirical models of the neutral atmosphere NRLMSISE-00 and thermospheric wind HWM07. The main factors determining Δf0F2 variations at middle latitudes during the storms were demonstrated to be the disturbed equatorward thermospheric wind transporting the disturbed atmospheric composition, the increase in the atomic oxygen concentration, and the passage of internal gravity waves. At low latitudes, the effects associated with neutral composition variations are less significant than those of the thermospheric wind and electric fields.

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    Tidelike Periodicities of Ionospheric Sporadic E Observed at Low Latitude Hainan Station
    Wang Guojun, Shi Jiankui, Wang Xiao
    2013, 33 (5):  501-508.  doi: 10.11728/cjss2013.05.501
    Abstract ( 1766 )   PDF (2637KB) ( 1384 )   Save

    The time series of the ionospheric Sporadic E (Es) critical frequency (f0Es) and its virtual height (h'Es) were performed on a large database of DPS-4 ionograms recorded at Hainan station (19.5°N, 109.1°E) in 2004 to investigate the features of tidelike periodicity variations in low latitude. On yearly spectra, there was pronounced 8-hour periodicity in low latitude Es in addition to the well known 24-and 12-hour tidal variations. The yearly average phases of 24-, 12-, and 8-hour periodicities for f0Es (h'Es) were at 13:00LT (13:00LT), 11:00LT (09:00LT), and 09:30LT (09:30LT). On every two-month spectra, the results showed that (1) the 24-hour periodicity in Es was the most pronounced in each season; (2) The 12-hour periodicity in Es was outstanding in each season except in January-February months; (3) The 8-hour periodicity was remarkable in equinoxes and July-August months for f0Es, and it was notable in almost each season for h'Es; (4) The 6-hour periodicity mainly occurred in November and December for f0Es, whereas for h'Es it appeared more in summer and winter, and weakly in equinox months. It is clearly distinct from previous results by the fact that the 6-and 8-hour periodicities in Es layer at Hainan station can occur in winter or other seasons. The 6-and 8-hour periodicities in Es layer most probably are caused by the quarter-diurnal and terdiurnal tide components, which needs to be investigated further by combining the observations and modeling of local tide.

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    Comparison of the Thermospheric Densities Between GRACE/CHAMP Satellites Data and NRLMSISE-00 Model
    Chen Xuxing, Hu Xiong, Xiao Cunying, Wang Xijing
    2013, 33 (5):  509-517.  doi: 10.11728/cjss2013.05.509
    Abstract ( 2177 )   PDF (2414KB) ( 1922 )   Save

    NRLMSISE-00 model is widely used in orbit determination and prediction of low-Earth orbit satellites. In order to calibrate the atmospheric density of NRLMSISE-00, the density errors of the model were analyzed by comparing with the observations from GRACE and CHAMP satellites. The density of the model was generally larger than that observed by GRACE and CHAMP satellites, especially under low solar activity. The density of the model showed higher accuracy at high latitude and its error varied with latitude and longitude. At the same location on the same orbit, density error of the model varied with local time and reached its maximum at 02:00LT and 15:00LT while reached its minimum at about 10:00LT and 20:00LT relatively. The 10.7cm solar radio flux (F10.7 index) showed high correlation with the density errors. The density of the model showed low accuracy during the solar minimum while good accuracy during the solar maximum. The model density showed better result at CHAMP satellite orbit with lower altitude comparing to the GRACE orbit. The error has less correlation with ap index during relatively quiet period of geomagnetic field (ap< 27).

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    Removing Solar Radiation Based on the Empirical Mode Decomposition Method for Seismo-Ionospheric Anomaly Before the M9.0 Tohoku Earthquake
    HU Yanli, XU Tong, WU Jian
    2013, 33 (5):  518-524.  doi: 10.11728/cjss2013.05.518
    Abstract ( 1969 )   PDF (2583KB) ( 1994 )   Save

    The ionospheric effect from solar activity can be seen as the background in the process of detecting the ionospheric precursor prior to strong earthquakes. The ionospheric variation induced by the forthcoming earthquake can be covered by the strong solar background during the period of high solar activity. The issue of how to remove the ionospheric effect from solar radiation is of outstanding significance. In this paper, a method of Empirical Mode Decomposition (EMD) is used to eliminate the solar background. As a case study, the global ionospheric map TEC before the M9.0 Tohoku earthquake on 11 March 2011 is analyzed. After the effect of solar radiation is removed using the EMD method, the precursor of the imminent earthquake is more obvious. The ionospheric anomaly had a local character and only appeared close to the earthquake epicenter while the useful signals were covered by the solar radiation background with traditional method, which implies that the EMD method is effective in eliminating solar radiation background.

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    Periodic Variations of Drag Coefficient for the ANDE Spherical Satellites During its Lifetime
    QI Yalong, LI Huijun, XIANG Jie, MAN Haijun
    2013, 33 (5):  525-531.  doi: 10.11728/cjss2013.05.525
    Abstract ( 1946 )   PDF (1860KB) ( 1541 )   Save

    A drag coefficient (CD) inversion method is introduced to study the variations of the drag coefficient for orbital satellites with spherical geometry. Drag coefficients of the four micro satellites in the Atmospheric Neutral Density Experiment (ANDE) are compiled out with this new method. The Lomb-Scargle Periodgram (LSP) analysis of the four ANDE satellites' CD series has shown that there are obvious 5, 7, 9, and 27 days' period in those data. Interesting results are found through comparing the LSP analysis with series of the daily solar radio flux at 10.7 cm (F10.7 index), the Ap index, and the daily averaged solar wind speed at 1AU. All series in the same time interval have an obvious period of about 27 days, which has already been explained as the association with the 27 days' solar rotation. The oscillating periods less than 27 days are found in series of CD, Ap and solar wind speed at 1AU, e.g., the 5, 7, 9 days period. However, these short periods disappeared in the time series of F10.7 index. The same periodicities of 5, 7, 9 days in Ap and solar wind are presented at the same time interval during the declining phase of solar cycle 23. While in the ascending phase of solar cycle 24, these short oscillations are not so obvious as that in the declining phase of solar cycle 23. These results provide definite evidence that the CD variations with period of 5, 7 and 9 days are produced by a combination of space weather effects caused by the solar wind and geomagnetic activity.

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    Study of Magnetospheric Shielding Effect With Energetic Particles Data From Chang’E-1
    Wang Jie, Qin Gang
    2013, 33 (5):  532-539.  doi: 10.11728/cjss2013.05.532
    Abstract ( 1765 )   PDF (621KB) ( 1288 )   Save

    Since about one fourth of the lunar orbit is inside the terrestrial magnetosphere, whether the Earth's magnetosphere can provide substantial magnetic shielding for energetic particles in the lunar orbit or not is essential for preparing human's exploration on lunar bases. Chang'E-1 is China's first lunar satellite, which is in a polar orbit of approximately 200km above the Moon's surface. In this paper, the data of energetic particles flux measured by the High-energy Particle Detector (HPD) onboard Chang'E-1 is analyzed, and the flux of protons at different energy channels within the energy range of 4~400MeV inside and outside the Earth's magnetosphere is compared. It is found that there is no significant decrease in the flux of protons at all the energy channels when the Moon is within the Earth's magnetotail compared with that when the Moon is in the solar wind, which indicates that the terrestrial magnetosphere could not provide any substantial magnetic shielding for the space energetic particles in the lunar orbit.

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    Analysis and Test of Anti-Jamming Performance for DS/FH TT&C System
    Pan Dianfei, Cheng Naiping, Hao Jianhua
    2013, 33 (5):  540-547.  doi: 10.11728/cjss2013.05.540
    Abstract ( 1734 )   PDF (3142KB) ( 1330 )   Save

    Based on the Minimum Performance Constraint (MPC), a synthetic analysis method was presented for the DS/FH TT&C system under jamming conditions. This method can evaluate the anti-jamming performance more effectively and comprehensively. Taking three classical interference environments as example, i.e. tone jamming, pulse interference and highly dynamic condition, the effects of different jammings on MPC with varying parameters are investigated. To overcome the deficiencies such as too many steps, poor efficiency and high cost in the anti-jamming capability test, the testing order of the attributes is modeled as an optimal route problem using Ant Colony Optimization (ACO) algorithm. Simulation results show that the proposed analytical model is correct and effective. The conclusions are evaluated to be significant and referable for the choice of DS/FH TT&C system jamming test schemes.

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    Research and Development of an Impact Testing System for Space Docking Mechanism
    Han Wei, Huang Yiyong, Zhang Xiang, Chen Xiaoqian
    2013, 33 (5):  548-553.  doi: 10.11728/cjss2013.05.548
    Abstract ( 1563 )   PDF (797KB) ( 1206 )   Save

    In the paper, a new ground based impact experiment system is designed to study the impact phenomenon of probe-cone docking mechanism in the course of spacecraft docking. Firstly, the whole scheme of the system, which includes the composition of the experiment system, experiment process, experimental sample and design of related devices, is given. Then, the frequency characteristic of acceleration and the effect of initial velocity on the impact time are summarized by numerical simulation on the basis of Hertz contact law, and the essential principle to choose the accelerometer for the experiment system is concluded. At last, the experiments of low speed impact are carried out. The experimental results show that the design scheme can meet the demand for measuring the docking impact force.

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    A Method of Satellite Calibration for Radar’s System Error Based on Least-square Estimation
    Zhong Xia, Zhang Jianwei, Yu Hao
    2013, 33 (5):  554-560.  doi: 10.11728/cjss2013.05.554
    Abstract ( 1824 )   PDF (2473KB) ( 1765 )   Save

    It is important to calibrate the system errors of precise-measurement radar for the aim of ensuring its measurement precision. The satellite calibration method for radar system error is a new method by measuring optical tracking satellites. In this paper, the key algorithm of satellite calibration method based on least-square estimation is analyzed and deduced. Then, the satellite calibration system is designed. Finally, the algorithm is simulated, according to the value of radar system error parameter obtained with traditional calibration method, and the simulation results are analyzed. It shows that the satellite calibration technique based on least-square estimation method is effective.

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    Research on the Planning Method for Astronomy Observation Mission
    Wu Haiyan, Meng Xin, Zhang Yuzhu, Li Ligang
    2013, 33 (5):  561-568.  doi: 10.11728/cjss2013.05.561
    Abstract ( 1788 )   PDF (2112KB) ( 1359 )   Save

    Space science satellite's astronomy observation mission planning is a complex multi-objective optimization problem. A multi-objective model is proposed based on abstraction of the mission planning elements and the constraints. Three scheduling criteria are considered, including minimizing important tasks unscheduled time, resource cost and scan tasks unscheduled time. Furthermore, Multi-objective Observation Mission Planning Algorithm (MOMPA) is put forward using the proposed model. The MOMPA solves conventional observation mission planning problem using the iteration constrained adjustment in population evolutionary methods. In order to validate MOMPA's performance, the mission planning test cases are designed. The short-term test case has 12 tasks with one week's observation period and the long-term test case has 36 tasks with three months' observation period. These experiments are conducted and analyzed, and results showed that MOMPA is applicable to astronomy observation planning in various scales.

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    Fuzzy Neural Networks Sliding Mode Control and Active Vibration Suppression for Free-floating Space Flexible Manipulator
    WANG Zongyuan, CHEN Li
    2013, 33 (5):  569-576.  doi: 10.11728/cjss2013.05.569
    Abstract ( 1684 )   PDF (742KB) ( 4070 )   Save

    This paper discusses the trajectory tracking and vibration suppression of free-floating flexible space manipulator with uncertain system parameters. The conception of virtual control force is used to design a virtual desired trajectory which reflects both flexible vibration and rigid motion. Then, in order to steadily track the trajectories of the base's attitude and the joint angle, the adaptive non-singular terminal sliding mode controller is proposed to track the desired trajectory. The controller integrates the advantages of terminal sliding mode technique, Fuzzy Wavelet Neural Network (FWNN) with good function approximation characteristic and robust control technology to process approximate error. In addition, adaptive algorithm is adopted for fuzzy wavelet neural network to adaptively adjust its all network weights and parameters, so the controller has strong robustness. Simulation results are given to illustrate the effectiveness of the proposed control scheme.

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