2015 Vol. 35, No. 2

Display Method:
Microwave Type U and RS Bursts in the X2.2 Solar Flare on 15 February 2011
XUE Yu, WANG Shujuan, YAN Yihua, HUANG Chong, YU Sijie, WANG Rui
2015, 35(2): 133-142. doi: 10.11728/cjss2015.02.133
Two groups of microwave type U and Reverse-Slope (RS) bursts after the Soft X-Ray (SXR) maximum were observed with the 2.6~3.8GHz spectrometer of Chinese Solar Broadband Radio Spectrometers (SBRS/Huairou) on 15 February 2011, when an X2.2 solar flare occurred in the Active Region (AR) NOAA11158. A Shear-driven Quadrupolar Reconnection (SQR) model was utilized to analyze these bursts and the two loops involved were found to be basically in the same spatial scale and have a height difference of about 1300km. These bursts were interpreted to be a result of a new reconnection process between the two similar-scaled loops.
Influence of ionospheric diurnal variation on the estimated GPS differential code bias
Li Lingxi, Zhang Donghe, Hao Yongqiang, Xiao Zuo
2015, 35(2): 143-151. doi: 10.11728/cjss2015.02.143
Abstract(1131) PDF 1120KB(1428)
The condition of smooth temporal and spatial change of ionosphere should be demanded in all the methods to estimate the GPS Differential Code Bias (DCB) from GPS observation. Nevertheless, because the ionosphere usually exhibits variation to different degrees, this condition is just an approximation. Therefore, it can be indicated that the stability of GPS DCB estimated from GPS observation is affected by the ionospheric status. With SCORE DCB estimation method and GPS data obtained at BJFS (middle latitude) and XIAM (low latitude) stations in 2001 and 2009, the satellites DCBs are estimated respectively. Especially, the influence of ionospheric diurnal variation on the DCB stability is verified. It is found that the condition of the ionospheric diurnal variation affects the stability of satellites DCBs estimated from GPS observations, and the satellite DCBs estimated from nighttime GPS data are more stable than that from daytime data. The stabilities of estimated DCBs from BJFS data in 2001 and 2009, and those from XIAM data in 2009 exhibit heavy dependence on local time, but the difference is not obvious for the DCBs estimated from XIAM data in 2001. XIAM station is located near the equatorial ionospheric anomaly, and the ionosphere of this region exhibits notable variations even in the nighttime in solar maximum phase. This may be the reason for the weak dependence of estimated DCBs on local time.
Using IGS-TEC data to analyze the variation of EIA crest over South China Region
Huang Linfeng, Jiang Yong, Wang Jingsong, Huang Jiang
2015, 35(2): 152-158. doi: 10.11728/cjss2015.02.152
Abstract(1235) PDF 2247KB(1387)
Variation of the Equatorial Ionospheric Anomaly (EIA) crest over South China region during the solar activity increasing periods is analyzed using the Total Electron Content (TEC) data from International GPS Service (IGS) between November 2010 and October 2011. The variation of the EIA crest in TEC shows an obvious seasonal and semiannual variation. Locations of the daily EIA crest have quite a large range of scatter in both universal time and latitude, but the similar seasonal or semiannual variation is not seen in the location of the anomaly crest. The variation of EIA crest in TEC shows a very good correlation with the solar flux, but do not correlate well with the geomagnetic activity.
Optimized Spherical Harmonic Function Model for Ionospheric Delay Correction
KANG Juan, WANG Ling, HUANG Wende
2015, 35(2): 159-165. doi: 10.11728/cjss2015.02.159
Abstract(941) PDF 967KB(1528)
Aiming at the ionospheric delay correction of single-frequency receiver, this paper proposes an optimized low-order spherical harmonic function model. Firstly, the description method of optimized ionospheric delay correction model is discussed and the objective and restraint condition of optimizing coefficients are defined. Then, according the characteristics that coefficients can be encoded, method and steps of using genetic algorithms to optimize coefficients are presented. Lastly, the accuracy analysis and comparison are made with Klobuchar based on the the ionosphere VTEC produced by CODE. The results show that accuracy of the optimized model is improved. It has an improvement about 1~2 TECU than the low-order spherical harmonic function model with the same number of coefficients and can better reflect the daily change of VTEC and the characteristics which vary with latitude.
Comparison of f0F2 between observation and the prediction based on IRI-2012 over Guangzhou
Wan Dehuan, Huang Jiang, Deng Baichang, Xu Jie, Kong Debao, Lin Guoguo
2015, 35(2): 166-177. doi: 10.11728/cjss2015.02.166
Abstract(1090) PDF 4011KB(1836)
Monthly mean values of f0F2 parameter, with an hour time interval resolution for diurnal variation, obtained at Guangzhou (23.2°N, 113.3°E) station are used to investigate the variations and comparisons with the International Reference Ionosphere (IRI-2012) model predictions. The results show that generally, IRI-2012 predictions follow well with the diurnal and seasonal variation patterns of the observed values of f0F2, and the predictions with CCIR coefficients is better than URSI. However, there are systematic deviation between observed values and IRI predictions with either CCIR or URSI coefficients. Generally IRI model greatly underestimates the values of f0F2 from about noon to sunrise of the next day, especially at 20:00LT, and slightly overestimates them from sunrise to about noon. The deviation will increase at the time when the nighttime enhancement occurred, especially in spring and autumn. This means that the predictions can not follow well with variation of the observed values of f0F2.
Full wave calculation of VLF wave penetrated into satellite altitude ionosphere
Zhao Shufan, Shen Xuhui, Zhang Xuemin, Pan Weiyan
2015, 35(2): 178-184. doi: 10.11728/cjss2015.02.178
Obvious anomalous VLF, ULF, SLF signals related with earthquake have been recorded by satellites. Research on finding electromagnetic anomaly in the ionosphere may become an important way for earthquake prediction. The calculation of VLF wave propagating in the ionosphere can provide theoretical results for extracting abnormal signals related with earthquake from satellite observation data. The ionosphere has been set to be lossy and anisotropic horizontal multi-layer media. The propagation matrix method had been used to solve the full wave equation. The reflection and polarization coefficient of two characteristic waves in the ionosphere has been calculated. The poynting flux and horizontal components of electromagnetic fields varying with altitude have also been simulated. The numerical results show that it is easier for the vertical polarized wave to penetrate into the ionosphere than parallel polarized wave. The left-handed polarization wave suffers severe attenuation in D region for the strong absorption. The right-handed polarization wave is transmitting mode, and the wave energy is saved in the magnetic field. The attenuation of the wave is lower when the frequency is smaller which means it may be more efficient for us to study the magnetic field of the lower frequency wave to find the electromagnetic abnormals of earthquakes.
Application in predicting the geomagnetic storm with variation characteristics of cosmic ray
Zhu Xiaolu, Xue Bingsen, Cheng Guosheng, Cang Zhongya
2015, 35(2): 185-191. doi: 10.11728/cjss2015.02.185
An algorithm is introduced to use the cosmic ray neutron detector data to predict great geomagnetic storms. The connection between cosmic ray and great geomagnetic storms and the relationship between cosmic ray stations are qualitatively analyzed. The neutron detector data from Irkutsk and Oulu stations are employed and wavelet denoising technology is used to improve the stability of the data. It is found that under the same conditions of universal time the correlation of the two stations is higher than quiet days during geomagnetic disturbances, while it is contrary under the same local time. Thus the variation in disturbed time and quiet time can be used to predict geomagnetic storms. The algorithm is specifically used to analyze the geomagnetic storm events in July 2004. It is found that before geomagnetic storm, relative fluxes of cosmic rays of Irkutsk and Oulu station became different. It can be used as a precursor of strong geomagnetic storms. Statistics with all relative events during March 2001 to May 2005 support an appropriate threshold related to the relative difference of cosmic ray about strong geomagnetic storms. It is tested with all events during September 2005 to December 2011 with the threshold. The result turned out to be encouraging with the accuracy rate reaching 87.5% (7 out of 8) and false forecast rate reaching 35.7% (5 out of 14).
Dynamic Distribution Features of Energetic Proton in South Atlantic Anomaly Based on the Observation of SAMPEX
LÜ Jingtian, ZHANG Xiaoxin, LIN Ruilin, HE Fei, JIANG Yong
2015, 35(2): 192-202. doi: 10.11728/cjss2015.02.192
After lots of experiments by using 19~27MeV differential energetic proton data based on the observation of SAMPEX from July of 1992 to June of 2004, it is found that the change of F10.7 and altitude have a great influence on the distribution of differential energetic proton flux in South Atlantic Anomaly. During the geomagnetic quiet time at 540±25km altitude, the energetic proton flux in South Atlantic Anomaly decreased with the increasing of F10.7, and the variation trend was flat when F10.7≥115sfu. It is found that there was obviously an anti-correlation between the absolute value of SYM-H and the differential energetic proton flux in South Atlantic Anomaly for storms with SYM-H<-50, and also there was a lasting effect on differential energetic proton flux in South Atlantic Anomaly. In addition, the proton flux could be significantly reduced in South Atlantic Anomaly during the main phase, while the proton flux showed a substantial resuming trend in the recovery phase of geomagnetic storms.
Implementation of adjoint/reverse monte carlo method in the analysis of satellites radiation
Lan Ting, Chen Dong, Chen Shanqiang, Shi Liqin, Liu Siqing
2015, 35(2): 203-210. doi: 10.11728/cjss2015.02.203
The Reverse Monte Carlo (RMC) method is a powerful biasing technique available in Geant4, also known as the Adjoint Monte Carlo method. In this method, particles are generated on the external boundary of the sensitive part of the geometry and then tracked backward in the geometry till they reach the external source surface, or exceed an energy threshold. By this way the computing time is focused only on particle tracks that are contributing to the tallies. The RMC method is much rapider than the Forward Monte Carlo (FMC) method when the sensitive part of the geometry is smaller compared to the rest of the geometry as well as the external source. Compared with the FMC method, accuracy of the RMC method applied to the radiation dose of the satellite is verified. Comparisons of RMC with the SHIELDOSE2, SSAT show that RMC is the preferred method of high-precision satellite radiation dose.
Influence of fluxgate magnetometer on the evenness of feedback magnetic field
Liu Nannan, Zhou Bin
2015, 35(2): 211-216. doi: 10.11728/cjss2015.02.211
Effects of the nonuniform feedback magnetic field on the fluxgate sensor is studied, and several typical types of the sensor are analyzed and compared mutually. It is required that the drive cores of fluxgate sensor should work in a uniform magnetic field in principle. When the magnetic field is nonuniform, error signal will be caused. Resultingly, the nonuniformity of the feedback magnetic field will lead to the change of fluxgate sensor's linear coefficient. Typical types of fluxgate sensors which work for space magnetic exploration include discrete form, Helmholtz form and Compacted Spherical Configuration (CSC) form, etc. The nonuniformity of the three feedback coils are analyzed as well as the performance of the fluxgate sensor when the feedback magnetic field is nonuniform. Compared to the simulation results, uniformity and stability of CSC sensor are much better than that of the discrete sensor, and CSC sensor is more conducive to the space magnetic field detection.
Optimization for distributed air loop in space science experiment platform
Ren Weijia, Chen Zifa, Tong Tiefeng, Sheng Qiang
2015, 35(2): 217-223. doi: 10.11728/cjss2015.02.217
Abstract(1029) PDF 4159KB(1046)
Space Science Experiment Platform is an integrated platform which can provide a suitable operating environment for the payload. The integrated platform mainly contains mechanical system, thermal control system, electronic system, and communication system. Forced air cooling is a principal method by using air as heat transfer medium of the integrated platform. In order to reduce the flow resistance of ventilation circuit and increase the air flow, three wind duct layouts of the distributed ventilation cooling circuit were designed. Meanwhile, by using Computational Fluid Dynamics (CFD) method, the pressure fields and velocity fields of these three wind duct layouts were calculated, and the system resistance and velocity distribution were also obtained. By trading-off the structures and the flow field resistance characters of three distributed air loop layouts, the optimized result of the distributed air loop in Space Science Experiment Platform was produced.
Thermal design and flight validation of HJ-1-C
Wang Lei, Wen Yaopu
2015, 35(2): 224-229. doi: 10.11728/cjss2015.02.224
Abstract(1176) PDF 1945KB(1282)
HJ-1-C is a Synthetic Aperture Radar (SAR) satellite of the Chinese Environment and Natural Disaster Monitoring constellation launched on November 19, 2012. The SAR payload uses mesh parabolic reflector antenna and solid-state transmitter to transmit high power in centralized manner. Based on the design concept that passive thermal control would be preferred over active thermal control for its simplicity and inherent reliability, HJ-1-C satellite thermal control system were provided in accordance with the HJ-1-C satellite working characteristics and space thermal environment on its orbit. The presentations about thermal design techniques, scheme and key problems solved are given. Moreover, onboard performance of the satellite on its orbit was analyzed. The flight telemetry data showed that the thermal control design was reasonable and well satisfied with the temperature requirements of the electronic equipments and payloads, which ensured the safety and reliability operation of satellite.
Spacecraft attitude disturbance optimization of space robot under multi-position restraint
Guo Chuangqiang, Ni Fenglei, Liu Hong
2015, 35(2): 230-236. doi: 10.11728/cjss2015.02.230
Optimization design of the path of the space manipulator tip is an economic and efficiency way to reduce the attitude disturbance on the basement arising from the motion of manipulator. However, research on the motion trajectory optimization for space robot under the condition of multi-position restraint in the Cartesian space is rare. In this paper, the motion trajectory was parameterized on the basis of revised cubic spline. Disturbance on the basement arising from the motion of manipulator was expressed by the objective function about the interpolating point of the spline and the migration time between two adjacent restrained positions. The global optimization of the objective function was realized using genetic algorithm. Simulation results indicated that the presented approach can effectively reduce the influence of disturbance on the attitude of basement, which was caused by the motion of manipulator. The designed trace in joint space is twice continuously differentiable.
A method of coverage analysis for multipoint coupling plasma detection on space processes
Yang Zhen, Li Yuanyuan, Gao Chen, Niu Wenlong, Meng Xin
2015, 35(2): 237-243. doi: 10.11728/cjss2015.02.237
So far the analysis method of detective coverage in multipoint coupling plasma detective missions on space processes is still at the stage of qualitative analysis. Statistical analysis of a certain space region for the satellites also cannot undergo further quantitative analysis. To meet the needs of fast development of space science missions, on the basis of correlation function and space processes analysis, a coverage analysis method based on θ-tR coverage diagram is proposed. By analysis of θ-tR coverage diagram in accumulative time period of various design alternative, the appropriate design can be chosen according to the characteristics of coverage range. Then quantitative analysis is made on multipoint coupling detective processes of two coplanar elliptic orbits, with which the method is verified.
In-orbit calibration of Haiyang-2 scatterometer using natural land-extended targets
Zhu Jintai, Dong Xiaolong, Wang Lei
2015, 35(2): 244-252. doi: 10.11728/cjss2015.02.244
Abstract(1014) PDF 1423KB(1150)
The scatterometer onboard Haiyang-2 satellite (HY-2 SCAT) is a rotating pencil-beam scatteromter. It provides 4 times of radar cross-section (σ0) measurements at different azimuth/incidence angles over a wind vector cell, in order to determine the near-surface wind field using the Geophysical Model Function (GMF). To achieve the required wind vector accuracy, radar cross-section measurements must be calibrated within a few tenths of a decibel (within 0.5dB). In this paper, HY-2 SCAT is calibrated using natural land-extended targets over different regions and is compared with OSCAT. σ0 errors over different azimuth angles are eliminated. The error sources of the measurements are analyzed and the pointing errors are compared with that estimated from measurements of Altimeter onboard HY-2 satellite.