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Table of Content

    15 September 2019, Volume 39 Issue 5 Previous Issue   
    Statistical Study on the Orientation and Type of Dynamic Pressure Pulses
    RUAN Mengsi, ZUO Pingbing
    2019, 39 (5):  573-581.  doi: 10.11728/cjss2019.05.573
    Abstract ( 466 )   PDF (6267KB) ( 143 )   Save
    Based on the Solar Wind Dynamic Pressure Pulse (DPP) events observed by the WIND spacecraft from 1995 to 2014, the distribution of the orientation and the type of DPPs is statistically analyzed. Firstly, the distribution of the angle △θ between the magnetic field vector in the preceding region and that in the succeeding region is well fitted by a piecewise function with double power-law distribution. Secondly, the Minimum Variance Analysis (MVA) method is used to determine the normal of DPP. In order to obtain a reliable normal of DPP, the MVA eigenvalue ratio λ2/λ3 ≥ 2 and △θ ≥ 30° are taken into constraints. The directions of the investigated DPPs mainly concentrate in a certain region of -50° ≤ θn ≤ 50°, 160° ≤ φn ≤ 250°, and the center of the investigated DPP is at the point of θ=-22.83°, φ=186.59°. Thirdly, DPP can be classified into four types of discontinuities such as Tangential Discontinuity (TD), Rotational Discontinuity (RD), Either Discontinuity (ED), and Neither Discontinuity (ND). The proportion of these four types of DPP is 46.37%, 19.57%, 27.49% and 6.57%, respectively. The results show that most DPP belong to TD, and the proportion of TD and RD are much larger than ED and ND during the solar minimum. The results would help to improve the accuracy of forecasting of the transit time between the WIND observation and the magnetosphere response and to study the formation mechanism of DPP.
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    F10.7 Index Forecasting Method Based on Area Statistics of Solar Active Regions
    YE Qian, SONG Qiao, XUE Bingsen
    2019, 39 (5):  582-590.  doi: 10.11728/cjss2019.05.582
    Abstract ( 390 )   PDF (6418KB) ( 90 )   Save
    Solar 10.7cm radio flux (F10.7) is an important indicator that reflects overall solar activity, which mainly comes from solar active regions. F10.7 index linearly correlates with the area size of the active regions. To improve the accuracy of F10.7 forecast, a new formula for F10.7 index prediction is proposed and evaluated, using the correlation between areas and F10.7 based on the classification of area size. The coefficients of the formula were calculated using the active region area data of SWPC and F10.7 index data of CSWFC from 2008 to 2018. Data of 2003 (active year) and 1997 (quiet year) were used to evaluate the formula. The results indicated the correlation coefficients between the predictions and the observations calculated by this formula were 0.9318 and 0.9295, both higher than the contemporary predictions of SWPC (0.9186 and 0.8771). This study utilized the active region areas on forecasting F10.7 for the first time and had improved the accuracy of F10.7 forecasting.
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    Twisted Coronal Mass Ejection on 4 August 2011
    YE Yudong
    2019, 39 (5):  591-602.  doi: 10.11728/cjss2019.05.591
    Abstract ( 494 )   PDF (13315KB) ( 44 )   Save
    On 4 August 2011, a GOES M9.3 flare with a fast coronal mass ejection was erupted from solar active region NOAA AR11261. After the flare, a rotating structure is observed by STEREO, in which the rotating motion lasted about 4 hours. The magnetic helicity flux associated with the flare was calculated based on the SDO/HMI vector magnetograms by tracking the plasma velocity of the photosphere. It is found that the photospheric shear and twist motion contribute significantly to the magnetic helicity injection before the flare. The coronal magnetic fields were extrapolated using the CESE-MHD-NLFFF code, which shows that twisted magnetic flux rope exists before the flare and disappears after the flare. With these analyses, a scenario for the formation and evolution of this eruption is suggested as follows. The rotation of the foot point on the west side of the eruption filament twisted the magnetic flux rope, and the highly twisted structure became unstable and erupted. During the eruption, it reconnected with open magnetic field lines near one leg, and a long duration of untwisting movement followed the eruption. Interestingly, the observations of WIND satellites at 1AU show characteristics of typical magnetic clouds in the corresponding interplanetary coronal mass ejections of this eruption, which indicates that a magnetic cloud might be a flux rope with one leg anchored on the Sun, and it is not previously considered.
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    Magnetic Flux Rope with a Complicated Core Field by a Cluster Case
    WANG Yang
    2019, 39 (5):  603-612.  doi: 10.11728/cjss2019.05.603
    Abstract ( 440 )   PDF (8035KB) ( 37 )   Save
    The Cluster spacecraft observed a magnetic reconnection event at the Earth magnetotail during 09:50 UT-10:50 UT on 28 August 2002. Cluster observed an evident quadrupole structure of the Hall magnetic field near the magnetic reconnection diffusion region. Due to the existence of the guide field, this quadrupole structure was distorted. During this reconnection event, Cluster observed a few magnetic flux ropes, and the polarity of the core field of most magnetic flux ropes is consistent with the polarity of the guiding field. However, one particular magnetic flux rope has a more complex structure of the core field than the others. In the core region of the flux ropes, the intensity peaks of the core field appeared there and its polarity is agreement with the guide field. Outside the core region, the polarity of the core field is opposite to that of the guide field. This complex structure of the core field within a flux rope has not been reported until now. Using the method of Minimum Directional Derivative (MDD), it is found that the flux rope was curved at the place where Cluster passed through. C1 and C3 satellites crossed the curved flux rope and detected the core field contrary to the guide field. C2 and C4 satellites situated on northward of C1 and C3 satellites, only crossed one part of the curved flux rope and thus detected the core field with a polarity consistent with the ambient magnetic field.
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    Numerical Study on High Frequency Radio Wave Heating Ionosphere F Layer Based on One-dimensional Model
    GAO Ze, FANG Hanxian, LIU Saisai, SUN Lingfeng, BAI Junshui, MA Jie
    2019, 39 (5):  613-622.  doi: 10.11728/cjss2019.05.613
    Abstract ( 482 )   PDF (5999KB) ( 69 )   Save
    Based on ionosphere one-dimensional heating model, the momentum equation, continuity equation and energy equation of electrons, and various parameter expressions are introduced. The heating process of ionosphere F layer is numerically solved by using the diagonal matrix pursuit method. During heating, the changes of electron density and temperature at different times are analyzed, the cases of heating ionosphere by radio wave with different frequency and power are also discussed. The results show that, when the ionosphere is heated by high frequency radio wave, the electron temperature increases rapidly, and soon approaches saturation. While the change of electron density is always slow, but the change range is more and more large during heating process. Under the influence of the geomagnetic field, the change of the electron density presents the hollow structure with the upper and lower dense structure, which is two peaks and one valley configuration. When radio wave heating ionosphere, the higher the frequency or the power is, the greater the change of electron density is. There is a suitable frequency which has the least influence on electron temperature.
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    Flow Field and Effects of SF6 Released in Ionosphere
    IE Shouzhi, ZHAO Haisheng, XUE Kun, XU Zhengwen
    2019, 39 (5):  623-628.  doi: 10.11728/cjss2019.05.623
    Abstract ( 389 )   PDF (4028KB) ( 64 )   Save
    The initial velocity and mass flow rate of sulfur hexafluoride (SF6) released in the ionosphere are key factors for the release effects research. They are not involved in traditional simulation models. In order to realize high precision simulation, the flow field in the storage vessel during SF6 release is studied. According to the structural size of the SF6 storage vessel, the geometric model is established, and the grid model uses structured grid and unstructured grid to discretize the computational area of the geometric model. Using the standard k-ε model and SIMPLE algorithm in the professional software Fluent, the temperature, pressure, velocity of flow and mass flow rate in the storage vessel during SF6 ionosphere release are simulated under different initial conditions, including initial temperature, pressure and filling mass. The flow field simulation results are taken as initial parameters in the three-dimensional refined model of SF6 ionosphere release, and the refined effects of SF6 ionosphere release are obtained.
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    Thermospheric Density Prediction Based on Electron Density Assimilation
    ZHANG Yanan, WU Xiaocheng, HU Xiong
    2019, 39 (5):  629-637.  doi: 10.11728/cjss2019.05.629
    Abstract ( 358 )   PDF (6327KB) ( 59 )   Save
    Using the thermosphere ionosphere coupling model TIEGCM and the thermospheric and ionospheric observations, the assimilation and forecast experiments with simulated and measured data are carried out based on the ensemble Kalman filter method respectively. The results of the simulated assimilation experiments with different thermospheric ionospheric parameters show that the temperature is the key parameter to improve the thermospheric density. In the assimilation experiments, the temperature is taken as the parameter of state vector. The optimization results show that the root mean square error of relative deviation of atmospheric density predicted by the model is reduced from 38% to 27% in 48 hours, and the stabilization time of assimilation is at least 30 hours. However, it may need at least 30 hours to achieve the best assimilation results when only the temperature is estimated, and the e-folding time of neutral density is 34 hours. The accuracy of the neutral density prediction in the TIEGCM has been significantly improved, which indicates that it is feasible to improve the prediction accuracy of the neutral density of the thermosphere using ionospheric observations
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    Analysis and Evaluation of High Accuracy Satellite Drag Model
    LIU Wei, GONG Jiancun, LIU Siqing, WANG Ronglan, LUO Bingxian
    2019, 39 (5):  638-647.  doi: 10.11728/cjss2019.05.638
    Abstract ( 570 )   PDF (6914KB) ( 51 )   Save
    The principle of Jacchia70 thermosphere model and the correction method of HASDM are analyzed. The partial derivative of mode density with respect to Spherical Harmonic coefficient (SH) is derived, and the specific process of solving spherical harmonic coefficient iteratively is given by means of mode density Taylor expansion. Based on the Accelerometer data of CHAMP and GRACE A/B satellites, one big geomagnetic storm event during 29 October 2003 was selected to test the validation of the method. The mean and stand deviation of relative errors are -81.7%, 74.4% and -5.9%, 53.1% before and after correction. It shows that this method is perfect. In the view of the upper and lower boundary temperatures of the thermal layer, and the principle of dynamic modification of the thermal layer model is analyzed in detail.The results provides a theoretical basis for the engineering practice of HASDM-like modification model.
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    Effect of Pressure and Power on Material Experimental Furnace in Space and on the Ground
    TANG Meibo, AI Fei, YANG Liping, PAN Xiuhong, WEN Haiqin, ZHANG Minghui, GAI Lijun, LEI Lei, DENG Weijie, CHEN Kun, LIU Yan, YU Qiang, LI Weining, ZHAO Xunfeng
    2019, 39 (5):  648-654.  doi: 10.11728/cjss2019.05.648
    Abstract ( 351 )   PDF (4828KB) ( 64 )   Save
    By analyzing the change of heating wires power in Tiangong-2 Material Experimental Furnace (TMEF) on the ground and in space, the equivalent pressure in the ground experiments is determined. Due to the gravity on the ground, the gas convection in TMEF has an important influence on the highest temperature of TMEF. The power ratio of the same experiments in space and on the ground is about 97.5% when the pressure in TMEF is 1atm. In space, the change of pressure in TMEF has weak effect on the highest temperature of the furnace. When the TMEF's pressure on the ground is 50% of 1atm in space, the obtained values (the powers and temperatures etc.) for the same experiments in space and on the ground are the same. These results are important to design the heating facility used in space.
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    Rigid Falling Sphere Technics in Air Observation
    AN Liangang, YANG Mingxing, QI Xin, WANG Ke, GUI Sujia
    2019, 39 (5):  655-661.  doi: 10.11728/cjss2019.05.655
    Abstract ( 413 )   PDF (4845KB) ( 48 )   Save
    In order to increase the height range of air observation, the rigid falling sphere technics is researched. Taking a 7-inch rigid falling sphere for instance, the trajectory simulation has been done. Along with the reference atmospheric data, the quantity of the acceleration that the sphere should bear is reckoned, showing the strict requirement for the acceleration measurement accuracy. The amount of interference of accessional portion of acceleration caused by lever arm effect is analyzed. Some drag calculation method and error are discussed and compared. The risk of EMC and the needs of miniaturized design are also considered. With the working principle of the rigid falling sphere and the analysis of its key technical features mentioned above, a type of rigid falling sphere design has been done, including the kinetic parameter measuring, the lever arm effect restraining, and the overall index design. One of the three rigid falling sphere manufactured and tested was launched, almost all of measuring data along the trajectory was obtained. Through the comparative analysis between the really measuring data acquired during the demonstration flight test and that resulted from the simulation, the technical proposal has been proved to be feasible and rational, and a clear path for further research is established.
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    Comparative Analysis of Two Precise Processing Methods for MGEX BDS Differential Code Biases
    MEI Dengkui, WEN Debao
    2019, 39 (5):  662-669.  doi: 10.11728/cjss2019.05.662
    Abstract ( 776 )   PDF (5293KB) ( 80 )   Save
    Differential Code Bias (DCB) is one of the systematic errors that must be dealt with in BDS-based high-precision positioning and ionospheric modeling. Firstly, two different processing strategies proposed by DLR and CAS for estimating BDS differential code biases are introduced respectively. Secondly, using the BDS differential code bias products released by MGEX in 2017 and June 2018, the variation characteristics of daily solutions, monthly mean values and the stability of BDS satellite DCB estimated by DLR and CAS, respectively, are compared and analyzed in this paper. The results show that both the DLR DCB and CAS DCB exhibited high stability in 2017, and the stability of C2I-C7I DCB was better than that of C2I-C6I DCB. Besides, the stability of monthly mean values of BDS satellite DCB was better than that of daily solutions. In June 2018, the stability of DLR DCB is slightly better than that of CAS DCB, and the difference between DLR DCB and CAS DCB ranged from -0.58ns to 1.07ns, indicating that the BDS satellite DCB estimated by CAS and DLR had a good consistency. BDS satellite DCB products provided by DLR and CAS have high reliability in correcting differential code biases for global BDS users.
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    Parameter Identification of Drag-free System Based on Extended State Observer
    ZHANG Chu, HE Jianwu, DUAN Li
    2019, 39 (5):  670-676.  doi: 10.11728/cjss2019.05.670
    Abstract ( 441 )   PDF (4471KB) ( 46 )   Save
    In this paper, in-orbit parameter identification problem of drag-free control system is studied. Since the drag-free system is not stable, it is necessary to design controllers to stablize this system, then the system can be identificated. According to the principle of active disturbance rejection control, the extended state observer is designed to estimate the disturbance and state of different control loops of the system. Based on the state and disturbance estimation values, the controller is designed to stabilize the system. A closed-loop parameter identification method for multi-input and multi-output systems based on extended state observer is proposed. In order to improve the identification effect in practical applications, the noise in the observed state is suppressed by introducing an integral filter, and the noise suppression mechanism is theoretically explained. Finally, this method is applied to a single-axis non-drag model similar to LISA Pathfinder, and the system dynamics parameters are estimated. The numerical simulation experiments have verified the validity and practicability of the proposed identification method.
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    Design and Analysis of a Wide Band Leaky Wave Antenna Based on Fractal
    ZHANG Lifang, WANG Hongjian, LIU Yang
    2019, 39 (5):  677-683.  doi: 10.11728/cjss2019.05.677
    Abstract ( 407 )   PDF (5517KB) ( 51 )   Save
    A planar wide band Leaky Wave Antenna (LWA) is proposed in this paper. The antenna is composed of two substrate integrated waveguide horns, the paraboloid structure and a microstrip patch array with 30×10 units. In order to obtain wide bandwidth and high gain, a Minkowski quasi-fractal is properly designed in each unit cell of the patch array. A comparison between two different designs of conventional patch and fractal patch has been done.The simulated results indicate that the LWA with fractal patches has the impedance characteristics with a frequency bandwidth of 18~22GHz for input return loss more than 10dB and a max gain of 17dB at 20GHz. The measured results show that the return loss of 18~22GHz is greater than 10dB and the peak gain at 20GHz is 14dB. The antenna has the advantages of small size, easy integration, high gain, wide band and beam scanning. It can be widely used in data transmission antenna of satellite.
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    Research on Rigid-flexible Coupling Dynamics of Flexible Cone-probe Docking Mechanism
    HAN Wei, JIANG Zhijie, HUANG Yiyong, CHEN Xiaoqian
    2019, 39 (5):  684-693.  doi: 10.11728/cjss2019.05.684
    Abstract ( 445 )   PDF (5570KB) ( 83 )   Save
    In this paper,a new kind of flexible cone composed of the thin-walled plates based on space probe-cone docking mechanism for small-sized spacecraft is presented.The theoretical model of docking impact dynamics,which takes into account the additional stiffness terms,is derived based on Lagrange Analytical Mechanics theory and Hertz contact theory.Finite element method is employed for the discretization of the thin-walled plate.The results show that the traditional dynamic model without considering the additional stiffness terms will be difficult to reach steady state.The method proposed in this paper can correctly predict the dynamic behavior of the system.
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    Design of Lossless Compression System for CCSDS On-board Data Based on FPGA
    SUN Jianwei, ZHANG Zhongwei, ZHENG Tie, XUE Changbin, CHEN Cong
    2019, 39 (5):  694-700.  doi: 10.11728/cjss2019.05.694
    Abstract ( 523 )   PDF (3945KB) ( 45 )   Save
    The growth volume of on-board data such as imagery, spectrum or radar data challenges the storage and transmission tasks on orbits. Hence, a universal lossless data compression algorithm is necessary. The lossless compression algorithm which is based on RICE code and recommended by CCSDS has an efficient performance for on-board data. However, the selection of parameter k consumes much time in this algorithm. In this paper, the method which uses maximum value of samples to optimize the parameter k can be adopted to reduce the complexity and the hardware resource. The proposed algorithm has the same compression ration but shorter run-time comparing with the traditional one. Finally, the proposed algorithm has been implemented by FPGA. The results of the simulation and experiment illustrate that the compression ratio of on-board data can reach 1.5 or more. It can fulfill the requirement of data compression for space borne system and spare more resources for the other payloads on the satellite.
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    Influence of Mars Channel Fading Characteristics on Communication Link Budget
    DU Yiying, YAO Xiujuan, FAN Yanan, YAN Yi, GAO Xiang
    2019, 39 (5):  701-708.  doi: 10.11728/cjss2019.05.701
    Abstract ( 459 )   PDF (6311KB) ( 141 )   Save
    The communication distance between Earth and Mars is far away, and there are many factors affecting the Mars communication link. In order to facilitate analysis and calculation, the Mars communication link is generally divided into three parts, the near Earth segment, interplanetary space segment, and near Mars segment. Focus on channel fading characteristics in the near Mars segment, the factors affecting Mars communication performance are extracted from Mars natural environment. Focus on theoretical analysis of the fading effect of Mars atmosphere, cloud and dust on the communication channel, and the actual Mars exploration mission of NASA is taken as an example to simulate the influence of above fading factors on communication link in the UHF, S, X and Ka band. Based on actual detection data, a model that suitable for Mars communication link budget is proposed on the premise of correcting the model of the Earth communication link budget. It can determine the range of Mars atmospheric fading, cloud fading and dust fading. The results can provide a reference for communication system design, link review and recalculation for Mars and other deep space exploration missions.
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