2014 Vol. 34, No. 6

Display Method:
Analysis of the Major Parameters in Solar Active Regions Based on PCA Method
SHEN Lin, DUN Jinping, ZHANG Xiaoxin, JIANG Yong
2014, 34(6): 765-772. doi: 10.11728/cjss2014.06.765
Abstract(829) PDF 922KB(1761)
Solar active region has close relationship with solar flares and solar proton events. In order to better understand the complicated relations between them as well as to build a concrete foundation for the forecasting of solar flares and solar proton events, the Principal Component Analysis (PCA) method is adopted to analyze the main parameters of solar active regions during 2007-2010. The parameters selected include sunspot magnetic classification, McIntosh classification, sunspot group area, 10.7 cm radio flux, flare index, the position of proton flares and soft X-ray flare intensity. A total of 81 principal component scores are obtained and compared with the solar proton event peak flow and annual average sunspot, 10.7 cm radio flux annual average, and it is found that the similarity is very high. The statistic results show that the principal component scores can represent the strength of solar activity to some extent.
Three-dimensional Steady State Interplanetary Solar Wind Simulation in Spherical Coordinates with a Six-component Grid
2014, 34(6): 773-784. doi: 10.11728/cjss2014.06.773
Abstract(1238) PDF 2843KB(1111)
In this paper, the MacCormack scheme is applied to the time-independent Magnetohydrodynamics (MHD) equations in spherical coordinates with a six-component grid for the three-dimensional interplanetary solar wind simulation. The use of six-component grid system can better body-fit the spherical shell domain of interplanetary space as well as avoid the singularity and the mesh convergence near the poles. The radial coordinate is treated as a time-like coordinate, thus can significantly reduce the computational time. The inner boundary distribution is determined by the empirical relations and observation. Five kinds of inner boundary conditions used formerly by MHD modelers are comparatively used to simulate the Carrington Rotation (CR) 1922 solar wind bac kground. The numerical results show that all these boundary conditions can produce consistent large-scale solar wind structure with the observation, and better result in agreement with observations can be achieved when adopting the following inner boundary condition: the radial speed is obtained by the empirical relationship proposed by McGregor et al. in 2011, the magnetic field is obtained by Horizontal Current Current Sheet (HCCS) model, an assumption of constant momentum flux is used to derive number density, and temperature is chosen to assure that the total pressure is uniform at the inner boundary.
Statistical study on the ascending time of solar energetic particle events
Jian Yi, Lai Min, Ding Liuguan
2014, 34(6): 785-793. doi: 10.11728/cjss2014.06.785
A total of 66 great gradual Solar Energetic Particle events (SEPs) from 1997 to 2006 were selected for analysis. The correlations were analyzed between the ascending time of the SEPs in time profile and the heliographic longitude of the source active region. The Coronal Mass Ejection (CME) and flares were also investigated in the ascending stage of the SEP flux profile. The results of statistical analysis indicate that the source regions of these great SEPs are mainly distributed in the western hemisphere, particularly within the area from 45° east longitude to 45° west longitude relative to the magnetic footpoint. In the presence of fast solar wind, the ascending time in low-energy channel has a good correlation with the relative longitude and the ascending time increases with the distance from magnetic footpoint. However, the correlation is unobvious in high-energy channel. Correlations have not been observed between the ascending time of the SEPs associated with full halo CMEs and the source region longitude. However, the relations between the ascending time of the SEPs and source longitude are well fitted with quadratic curves. The analytical results show that the flare acceleration process played an important role in the gradual phase of SEP time profile, especially for the SEPs associated with partial halo CMEs.
Nonadiabatic acceleration of protons in the near-earth magnetotail during substorm dipolarization
Meng Xuejie, Cao Jinbin, Wang Tieyan, Ma Yuduan
2014, 34(6): 794-801. doi: 10.11728/cjss2014.06.794
Abstract(733) PDF 651KB(1149)
Using test particle simulation, the acceleration of -Re~-5Re magnetotail protons is studied during substorm-associated dipolarization events. The effects of the ultra-low frequency waves on the proton acceleration process in the vicinity of equatorial plane are investigated. It is shown that particles are injected earthward during dipolarization. Protons with relatively low initial energies may not conserve their magnetic moment, and they are nonadiabatically accelerated by the electromagnetic wave whose frequency is close to the proton gyrofrequency. In addition, the final energies of the particles after the event are related to its initial energies at the dipolarization onset. For the protons whose initial energies are much lower than the cutoff energy, their energies are increased significantly after the event. The particles' energy increase have the same order of magnitude with the O+ ions' in the dipolarization process, and it is related to the electromagnetic wave frequencies. However, for the protons whose initial energies are higher than the cutoff energy, their final energy level is not influenced by the wave and the energies are stable during the injection.
Investigation of Ionospheric Scintillations over South China
ZUO Xiaomin, HUANG Jiang, XIA Chunliang, XU Jie
2014, 34(6): 802-808. doi: 10.11728/cjss2014.06.802
Abstract(1166) PDF 3342KB(1646)
Data recorded by GPS ionospheric scintillation monitors in Guangzhou (23.17°N, 113.34°E) and Maoming (21.45°N, 111.31°E) stations, which are situated near the northern crest of the equatorial ionosphere anormaly, has been used to study the day-to-day, month-to-month, local time and spatial variation characteristics of ionospheric amplitude scintillation during the period from July 2011 to June 2012. The results show that different intensity of amplitude scintillations has co mmon temporal variation characteristics. The scintillation activities with S4>0.4 and S4>0.6 mostly occur from 20:00LT to 24:00LT in spring and autumn. Spatially, scintillations distribute throughout the large region with the latitude from 18° to 27° and the longitude from 109° to 118° for Guangzhou and the latitude from 17° to 26° and the longitude from 107° to 116° for Maoming in the fall of 2011. However, scintillations mainly appear in a small area overhead in the spring of 2012 of both stations.
First Observation and Analysis of Seasonal Variation of the Ionosphere D Region Electron Density at Kunming
LI Na, CHEN Jinsong, DING Zonghua, ZHAO Zhenwei, WU Jian
2014, 34(6): 809-814. doi: 10.11728/cjss2014.06.809
The observed data by Kunming MF radar (25.6°N, 103.8°E) from August 2008 to July 2009 are employed to investigate the seasonal variation of the ionosphere D region electron density during low solar activity. The obvious characteristics in D region electron density is semiannual variation with the observed values larger in spring and autumn, smaller in su mmer and winter, which is different from the simulated result by International Reference Ionosphere (IRI). The result conforms to that observed by digital ionosonde. Then, comparison with that of zonal wind shows very good correspondence of changing trend between them. Finally the reasons leading to the correspondence are discussed.
Retrieval of initial disturbance of Spread-F based on adjoint theory and numerical simulation
Fan Xin, Fang Hanxian, Niu Jun, Weng Libin, Yang Xu
2014, 34(6): 815-821. doi: 10.11728/cjss2014.06.815
Abstract(851) PDF 888KB(1136)
Retrieval of initial disturbance of Spread-F is very important in the study on Rayleigh-Taylor instability (R-T instability). In this paper, adjoint theory is proposed and used in the retrieval of initial disturbance of Spread-F for the first time. The adjoint model of ionospheric instability is presented and numerical simulation is also carried out to test the algorithm. A physical model for the development of the mid-latitude Spread-F is developed, including the equations for density, momentum and continuity. The simulation results show that ionospheric instability model described the development of Spread-F well. By using different iterative initial value and simulated observation data at different time, the retrieval results fit well with the initial values, and it is feasible to obtain the initial disturbance using adjoint model.
Analysis on Ionospheric Perturbations before Yushu Earthquake
ZHANG Xuemin, LIU Jing, ZHAO Biqiang, XU Tong, SHEN Xuhui, YAO Lu
2014, 34(6): 822-829. doi: 10.11728/cjss2014.06.822
Abstract(1168) PDF 3347KB(1902)
In this paper, the ionospheric perturbations in three parameters have been analyzed around Yushu earthquake, including f0F2 from ionosonde, GPS TEC, and in-situ plasma parameters by satellite. Their temporal and spatial relationship with this event were studied, and the results showed synchronous disturbances in multi-parameters on 13 April, just one day before the Yushu earthquake. The f0F2 abnormally increased 40% relative to its sliding median of 5 days before, and its anomalous center moved from southeast to southwest. GPS TEC with abnormal amplitude of 15TECU (1TECU=1016m-2) concentrated in a longitudinal scale of 15° over the south of the epicenter, and similar anomalies were found at its conjugate areas. While the in-situ observation of oxygen ion density Ni(O+) from DEMETER reached its maximum on April 13 for the four months from January to April in 2010, with the anomalies deviating to the equatorial areas but limited in the longitude scale of 30°-50°. Su mming up the anomalous characteristics in these three parameters, whatever the local feature in space, or the close relevance in time, both exhibited possible relationship with the Yushu earthquake. Combined with other observations, the seismo-ionospheric coupling mechanism was discussed during the preparation process of Yushu earthquake.
A Method of Calibrating Thermosphere Density Based on Temperature Parameters
LI Xie, TANG Geshi, LI Zheng, LI Cuilan, LIU Shushi
2014, 34(6): 830-836. doi: 10.11728/cjss2014.06.830
Abstract(1439) PDF 2766KB(1682)
Thermosphere atmospheric drag is the significant factor affecting most space operations of low Earth orbiter, especially, an inherent 15% formal error of empirical models has become the cumber to improve orbit calculations accuracy. Among the empirical models used in aerospace engineering, JACCHIA71 model, which has relative explicit physical bac kground and less parameters, is selected as a basic model. The temperature Tc and Tx, namely nighttime minimum of the global exospheric temperature and inflection point temperature, are chosen as the estimated parameters during the differential correction. The condition equation of density with respect to these two temperatures is established, and the least square solutions are given as well. The model accuracy improvement is almost enhanced by over an order of magnitude after calibration using CHAMP data. Orbit prediction accuracy of TG01 with the position bias of 2 km is also improved to 1.3 km through temperature corrections using in-site detecting data. All of these case studies validates the effectiveness of the calibration algorithm.
Research on active plasma release experiment in ionosphere
Wang Jindong, Li Lei, Tao Ran, Liu Cheng, Liu Yue, Cheng Bingjun, Xie Lianghai
2014, 34(6): 837-842. doi: 10.11728/cjss2014.06.837
Barium release is one kind of active experiments for space physics research, which can be used to study the near-earth space environment efficiently. In April 2013, the first barium release experiment of China was successfully implemented by Center for Space Science and Applied Research, Chinese Academy of Sciences, in Hainan Province. Nearly 1 kg barium was released by a sounding rocket at 190 km height in this experiment, which produced a spherical cloud including barium atoms and ions. The evolution process of barium cloud was recorded by ground-based optical observatory, obtaining the whole process of barium cloud brightness, particle density, composition and diffusion range variation with time. Through analysis of barium cloud drift, the neutral wind field characteristics of low-latitude regions of the ionosphere at the point of release are obtained. It is useful for further study of dynamics in low-latitude ionosphere region.
Magnetic field detection method of China seismo-electromagnetic satellite
Zhou Bin, Cheng Bingjun, Zhang Yiteng, Zhang Zhenqi, Wang Jindong, Li Lei
2014, 34(6): 843-848. doi: 10.11728/cjss2014.06.843
Abstract(1023) PDF 2220KB(1321)
China Seismo-Electromagnetic Satellite (CSES) is the first domestic satellite for electromagnetic science experiment in near Earth orbit. Space magnetic field detection is one of the primary scientific objectives of CSES, which is based on long-term steady vector magnetic measurement. Flux-gate magnetometer and Coupled Dark State magnetometer are employed to detect vector and scalar magnetic field respectively. Using fitting method, we could get absolute accuracy data of vector magnetic field. A method about flux-gate magnetometer vector data calibration is introduced using scalar magnetic field data, and it ensures the accuracy of vector magnetic field data. The performance of this method is evaluated by simulation, and it gives an accuracy of 1 nT.
A New Design for Digital Ionosonde
WANG Shun, CHEN Ziwei, ZHANG Feng, GONG Zhaoqian, FANG Guangyou
2014, 34(6): 849-857. doi: 10.11728/cjss2014.06.849
Abstract(1012) PDF 3661KB(1266)
In this paper a new design for digital ionosonde is presented based on the concept of directly sampling in the RF domain, and the real time digital down-conversion processing is implemented in FPGA device, which improves the signals identity of I and Q, and enhances the dynamic range of the receiver. In addition, since the digital waveform generation in transmitting path, the digital down-conversion processing in receiving path, data pre-processing, and timing control functions of the whole system are integrated in one FPGA chip, which improved the flexibility of the ionosonde. To verify the design, a high quality digital ionosonde called CAS-DIS (Chinese Academy of Sciences, Digital Ionosonde) has been developed. This paper describes the details of CAS-DIS, its main features and testing results in the ionosphere detection, including in Wuhan ionospheric sounding and calibration station and Wuhan-Beijing oblique ionospheric sounding system, and the observations show that performance of the iononsonde using the proposed design is superior, and the ionosonde can operate in both vertical and oblique sounding mode, to meet a variety of applications in ionospheric detection.
Research on characterized graphics matching method of autonomous optical navigation for lunar explorer
Mu Rongjun, Gao Mingyang, Liu Bin, Hu Ying
2014, 34(6): 858-866. doi: 10.11728/cjss2014.06.858
This paper focuses on the characterized graphics matching based navigation method of precise landing on the moon, which mainly consists of feature point extracting, characterized graphics constructing and matching. Based on the property that the relative distance between two characterized points is unchanged, by establishing the connected rules of two characterized points, the method is adopted to overcome the problem of graphics matching with translation, rotation and scale changes. The algorithm is tested with multiple real lunar pictures, and the emulational experiment results approve the effectiveness of the method. Navigation method based on the characterized graphics matching is validated by designing a numerical simulation. The simulations reveal that the method that can gain the position and speed of vehicle with high precision in nearly real-time is an effective solution to lunar precise landing.
An Improved Double r-iteration IOD Method for GEO UCTs Based on SBSS System
TANG Yi, ZHONG Wenan, LI Shuang, SHOU Junming
2014, 34(6): 867-871. doi: 10.11728/cjss2014.06.867
Abstract(1213) PDF 399KB(1633)
The purpose of initial orbit determination, especially in the case of angles-only data for observation, is to obtain an initial estimate that is close enough to the true orbit to enable subsequent precision orbit determination processing to be successful. However, the classical angles-only initial orbit determination methods cannot deal with the observation data whose Earth-central angle is larger than 360°. In this paper, an improved double r-iteration initial orbit determination method to deal with the above case is presented to monitor geosynchronous Earth orbit objects for a spacebased surveillance system. Simulation results indicate that the improved double r-iteration method is feasible, and the accuracy of the obtained initial orbit meets the requirements of re-acquiring the object.
Station-keeping control of solar sail Lissajous orbit with attitude angles amplitude constraint
Zhang Hui, Zhu Min, Zhou Jianliang, Wang Yong
2014, 34(6): 872-880. doi: 10.11728/cjss2014.06.872
The orbital dynamic equations of solar sail spacecraft have non-affine and nonlinear properties with attitude angles as the station-keeping control input. The linearization method has been widely used in settling down station-keeping problem of solar sail spacecraft orbit. However, the linear model, obtained from local linearization around the libration point, inherently has the approximate scope which results in the constraint of the orbit amplitude as well as the constraint of the attitude angles amplitude. In this paper, the model error of solar sail linear dynamic system is presented and the constraint of attitude angles amplitude is calculated. As a result of the controller amplitude constraint, the trajectory control ability is bounded, raising questions about the maximum allowable orbit injection error. Then, the controllability Gramian matrix is used to estimate the maximum allowable orbit injection error. Furthermore, the Linear Quadratic Regulator (LQR) controller considering maximum allowable orbit injection error is designed and applied to solar sail CR3BP nonlinear model. The numerical simulations indicate that Lissajous orbit injection error convergence as well as 20 years' orbit station-keeping with high precision have been realized.
Optimal control for state-keeping stage of tethered satellite with random perturbation
Wang Changqing, Zhang Malin, Wang Wei, Li Aijun, Y Zabolotnov
2014, 34(6): 881-886. doi: 10.11728/cjss2014.06.881
Abstract(1058) PDF 633KB(10660)
The dynamic equations of a Tethered Satellite System (TSS) with elastic tether were established. This model was linearized at the equilibrium position, and the influence of random perturbation on TSS was considered. In order to fulfill the station-keep control of the TSS along orbits, by integrating Kalman filter with the optimal state feedback control, a control scheme based on the 2nd Young Engineers' Satellite (YES2) project was proposed. Finally, simulation analyses based on the models with considering elasticity and neglecting elasticity were made respectively. Simulation results show that the system under proposed law has good anti-ja mming performance. Besides, the tether tension changes smoothly and its amplitude is small, so that the TSS has superior reliability and security. And with the decrease of stiffness, the tether longitudinal vibration increases, which could provide ideas for selecting the appropriate tether material.
Star position correction of dynamic star simulator based on distortion effect
Sun Gaofei, Zhang Guoyu, Liu Shi, Gao Yujun, Xu Ke
2014, 34(6): 887-893. doi: 10.11728/cjss2014.06.887
In order to realize the testing and calibrating of star sensor spectral detection capability, a set of ground calibration system which can simulate the stellar spectra is developed, and the stellar simulation accuracy is required to be better than 10%. Spectral distribution controllable and light intensity adjustable light simulation system is adopted to be the core device to simulate changes in stellar spectra, collimating optical system with high image quality is designed to make the star map exit parallel light and present the star map at the exit pupil of optical system, then the high accuracy star map simulation with stellar spectra information is completed. Finally, using Lighttools, the spectral simulation model of calibration system is established and simulation results show that the stellar spectra simulation accuracy is better than 10%.
Structure Design and Thermal Deformation Analysis of Large Spaceborne Flat Slotted Antenna
FAN Wenjie, LI Xiaopeng, CHEN Bo
2014, 34(6): 894-898. doi: 10.11728/cjss2014.06.894
Large spaceborne flat slotted antennas recently boom rapidly in the field of space applications. The structural element of large flat slotted antenna is introduced. A new connected scheme of antenna is put forward and unidirectional floating fixing method is applied to outside four flange of antenna. This fixing method could ensure that antenna move along one certain direction freely when temperature rises or drops. Thermal deformation is analyzed in ultimate high temperature and ultimate low temperature. The results are thermal deformation RMS value in Y direction decreases from 0.53 mm to 0.3 mm in ultimate high temperature and decreases from 0.33 mm to 0.1 mm in ultimate low temperature. It shows that the thermal deformation RMS values satisfy the design requirements on board, so electrical performance can be assured.