Table of Content

    15 January 2019, Volume 39 Issue 1 Previous Issue    Next Issue
    Near Earth Vortices Driving of Field Aligned Currents Based on Magnetosphere Multiscale and Swarm Observations
    2019, 39 (1):  9-17.  doi: 10.11728/cjss2019.01.09
    Abstract ( 564 )   PDF (2284KB) ( 450 )   Save

    A long-standing mystery in the study of Field-Aligned Currents (FACs) has been that:how the currents are generated and why they appear to be much stronger at high altitudes than in the ionosphere.Here we present two events of magnetotail FACs observed by the Magnetospheric Multiscale Spacecraft (MMS) on 1st July and 14th July 2016,to show how the Substorm Current Wedges (SCW) were formed.The results show that particles were transferred heading towards the Earth during the expansion phase of substorms. The azimuthal flow formed clockwise (counter-clockwise) vortex-like motion,and then generated downward (upward) FACs on the tailward/poleward side of the distorted field with opposite vorticity on their Earthward/equatorward side.We also analyzed the Region 1 FACs observed by the Earth Explorer Swarm spacecraft on 1st July 2016 and found that they were associated with FACs observed by MMS,although differing by a factor of 10.This difference suggests that either there was the closure of the currents at altitudes above 500 km or the currents were not strictly parallel to B and closed at longitudes away from where they were generated.

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    Statistical Model of the Relativistic Electron Fluence Forecast at Geostationary Orbit
    ZHONG Qiuzhen, WEI Lihang, LIN Ruilin, ZHENG Jinlei, LIU Siqing
    2019, 39 (1):  18-27.  doi: 10.11728/cjss2019.01.018
    Abstract ( 711 )   PDF (1985KB) ( 384 )   Save

    Based on the theory of local acceleration by chorus mode wave, AE index is selected as a good indicator for both source electron flux and flux anisotropy, and Dst index is selected as a good indicator for relativistic electron loss. By use of AE and Dst indices as input parameters, a prediction model for relativistic electrons at GEO orbit has been established on the basis of linear filter technology. The results are as follows. The total Prediction Efficiency (PE) of our model for the data from 2000 to 2009 is 0.818. The highest PE is about 0.856, which occurred in 2009. The lowest PE is about 0.663, which occurred in 2003. The prediction accuracy of the model is significantly better than that of the persistence model and is slightly less than the model developed by the same method but taking the solar wind as the input parameters. Furthermore, the model is improved by taking solar wind speed as an additional input parameter. The values of PE from 2000 to 2009 increase every year. The PE of 2005 is increased by 9.5%. The total prediction efficiency from 2000 to 2009 increased to 0.848. The linear correlation coefficient between forecasts and observations is 0.918, and the root mean square error is 0.422.

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    Extreme Value Model of Mid- and Low-latitude Geoelectric Field Due to Magnetic Storms
    WU Weili, ZHAO Puzhi, CAI Qidong
    2019, 39 (1):  28-35.  doi: 10.11728/cjss2019.01.028
    Abstract ( 450 )   PDF (1266KB) ( 362 )   Save

    Estimation for the level of extreme geoelectric field can provide a basis to quantify the risk of the grounding technology systems due to magnetic storms. The extreme value model of geoelectric field is presented on the basis of the EVT. Firstly, the years maximum sample data of geoelectric field are constructed by using the geomagnetic data, and the general Pareto distribution model is established. Secondly, the model is examined by the mean residual life plot and the Q-Q plot, and the parameters are estimated by Bayes method. Finally, the return period i.e., geoelectric field extreme value, was calculated. The 52 years' data of geomagnetic storms and the Earth resistivity model of Shache, Xinjiang are used to estimate the geoelectric field. The geoelectric field of 50-year is 3.288V·km-1 and that of once-in-a-century is up to 3.332V·km-1 in mid- and low-latitude area. By contrasting with the existing literature analysis, the credibility of model is validated.

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    Beidou Navigation Satellite System Sounding of the Ionosphere from FY-3C GNOS:Preliminary Results
    YANG Guanglin, SUN Yueqiang, BAI Weihua, ZHANG Xiaoxin, YANG Zhongdong, ZHANG Peng, TAN Guangyuan
    2019, 39 (1):  36-45.  doi: 10.11728/cjss2019.01.036
    Abstract ( 743 )   PDF (2815KB) ( 423 )   Save

    The world's first dual-system compatible Global Navigation Satellite System (GNSS) Occultation Sounder (GNOS) for Beidou Navigation Satellite System (BDS) and Global Positioning System (GPS) was successfully launched into orbit with FY-3C satellite on 23 September 2013, and a large number of ionospheric BDS Radio Occultation (BDSRO) data have been collected. The ionospheric BDSRO products observed by FY-3C GNOS are introduced firstly, then the distribution of ionospheric Electron Density Profiles (EDPs) in October 2013 is analyzed. Finally, the precision of ionospheric BDSRO data obtained by FY-3C GNOS is verified through F2-layer peak electron density (NmF2) comparisons between BDSRO and ionosondes. The results show that the correlation coefficient ofNmF2 data between BDSRO and ionosondes is 0.96, the bias is 10.21% and the standard deviation is 19.61%, which is comparable with other international ionospheric occultation products based on GPS. The NmF2 precision of BDSRO has the following characteristics. Its precision at daytime is higher than that at nighttime, and its precision in summer is higher than that in equinox seasons, while the precision in winter is lowest. Moreover, its precision at mid-latitude region is higher than that at low-latitude region, and the precision at high-latitude region is lowest. The precision of BDS satellites on Inclined Geosynchronous Satellite Orbit (IGSO) is higher than that on Geosynchronous Orbit (GEO) and Medium Earth Orbit (MEO). The precision consistency of the ionospheric occultation product between BDS-FY-3C GNOS and other internationl occultation projects is of great significance for comprehensively utilizing the GNSS occultation observation data. With the continued deployment of FY-3 satellites and Beidou navigation satellites, GNOS can provide more ionospheric occultation data in the future, which will be helpful to the ionospheric research and space weather forecasting based on GNSS occultation observations.

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    Ionospheric Delay Correction of Single-frequency for Global Navigation Satellite System Based on NTCM-BC Model
    HU Hanjing, WANG Xiaoni, LIU Junting
    2019, 39 (1):  46-54.  doi: 10.11728/cjss2019.01.046
    Abstract ( 598 )   PDF (1990KB) ( 340 )   Save

    Ionospheric delay is one of dominant factors that affect single-frequency positioning accuracy of Global Navigation Satellite System (GNSS). It is very important for GNSS single-frequency users to study the ionospheric delay correction model of high accuracy. In this paper, an ionospheric correction algorithm called Neustrelitz TEC Broadcast model (NTCM-BC) is chosen as the single-frequency ionospheric delay correction model. The correction coefficients of NTCM-BC model are obtained by non-linear least square fitting method based on the 1-day predicted ionospheric maps (COPG file). The results of NTCM-BC model have been compared with Klobuchar model and IGSG's Global Ionosphere Maps (GIM). It can be concluded that, for solar maximum, moderate or minimum, NTCM-BC model can achieve a significantly better performance than Klobuchar model in global average. The mean error and Root Mean Square Error (RMSE) of TEC calculation decrease by 41% and 30%, respectively. The TEC deviations of the two models have positive correlations with solar activity. Compared with the geomagnetic quiet days, the errors of Klobuchar and NTCM-BC models will increase during the geomagnetic perturbed days. Moreover, the correction error depends on latitude, season and local time.

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    Radio Propagation Model of Ionospheric Sporadic E
    ZHANG Yabin, WU Jian, XU Zhengwen, XU Bin, XUE Kun, ZHAO Haisheng, CUI Yuguo
    2019, 39 (1):  55-61.  doi: 10.11728/cjss2019.01.055
    Abstract ( 502 )   PDF (1228KB) ( 352 )   Save

    Considering the influence of atmospheric refraction, the relationship between the great-circle propagation distance and the elevation angle under different height Es layers is calculated. Based on the numerical model of ion density of the Es layer, and using an autocorrelation function of the fluctuation of electron density given by modified Bessel functions of the fifth, the reflection and scattering models are built considering the scale of irregularities. The relationships between the attenuation of the VHF oblique incident propagation of the Es layer and the frequency are simulated by the models. For the reflection model, the thicker the Es layer is, the greater the attenuation is. For the scattering model, the larger the vertical and horizontal drift scale are, the greater the attenuation is under the same horizontal scale of Es layer irregularities. However, if the vertical and horizontal drifts are same, the attenuation is inversely proportional to the horizontal scale. In reflection and scattering models, the higher the f0Es is, the smaller the attenuation is while the higher the operating frequency of radio waves is, the greater the attenuation is. The results also agree well with the observations of Es propagation path. Es reflection/scattering mechanism is clear for different intensity of ionosphere.

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    Comparison between the Electron Capture Capacity of SF6 and CF3Br
    BAI Yun, SHI Hongxing, ZHAO Jing, WANG Geng, CHEN Yankun
    2019, 39 (1):  62-68.  doi: 10.11728/cjss2019.01.062
    Abstract ( 416 )   PDF (1487KB) ( 342 )   Save

    The sulfur hexafluoride (SF6) and trifluoromethane (CF3Br) are two kinds of ionospheric modification agents. The GC-ECD and DFT evaluation method for vacuum electron absorption are designed, and two methods are used to evaluate the SF6 and CF3Br. Finally, the results of two methods are compared and analyzed. The results of GC-ECD evaluation method show that SF6 and CF3Br have better response on ECD detector, and the response of CF3Br on ECD detector is stronger than that of SF6. The results of DFT evaluation method show that both SF6 and CF3Br have superior electron absorption capacity. Considering the results of the GC-ECD and DFT evaluation method, it can be seen that both SF6 and CF3Br have obvious electron absorption capacity and have superior electron absorption effect. The electron absorption effect of CF3Br is superior to that of SF6.

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    Formation Mechanism of Sub South Atlantic Anomaly Region Observed by FY-3A
    MA Jie, XUE Bingsen, FANG Hanxian, WENG Libin, ZHOU Yaqin, XIA Jilu, LU Xiaoshan, SUN Zhiqiang
    2019, 39 (1):  69-75.  doi: 10.11728/cjss2019.01.069
    Abstract ( 629 )   PDF (4126KB) ( 322 )   Save

    Based on the proton flux distribution in the inner radiation belt obtained by FY-3A, it is found that the 3~5MeV energy channel shows a second anomalous region besides the South Atlantic Anomaly region. The anomaly zone is a sub-extreme area of proton flux, compared with the main South Atlantic Anomaly region, the new proton flux extremum is weaker and smaller, so it is called the sub South Atlantic Anomaly region. By selecting representative sample points in the main South Atlantic anomaly and sub South Atlantic anomaly areas, the formation mechanism of the sub South Atlantic Anomaly region is studied. The results show that the inner radiation belt proton flux approximately normally distributes with pitch angle, proton fluxes appear at a maximum near the 90° pitch angle; when the pitch angle is greater than 120° or less than 60°, the proton flux is almost zero. In addition, the proton flux in the main South Atlantic Anomaly region is completely anisotropic in each energy channel, and the proton flux in the sub South Atlantic Anomaly region tends to be isotropic as the energy channel increases. And this phenomenon is further verified by the NOAA observation data. Moreover, it is used to explain the formation mechanism of the sub South Atlantic Anomaly region.

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    Comparison of Retrieval Methods for Neutral Wind Based on Airglow Measurements by a Ground-based Fabry-Perot Interferometer
    YANG Run, XU Jiyao, ZHU Yajun, YUAN Wei
    2019, 39 (1):  76-83.  doi: 10.11728/cjss2019.01.076
    Abstract ( 474 )   PDF (1355KB) ( 317 )   Save

    Three methods are used to derive neutral winds from mid- and upper atmospheric airglow measurements by a ground-based Fabry-Perot Interferometer (FPI), which was deployed at Xinglong station (40.2°N, 117.4°E) in Hebei province. The three methods are the radius method, the complete Fourier series description method and the nonlinear regression fitting method, respectively. The retrieval results show that the three methods can derive the neutral winds correctly within a given range of error. The nonlinear regression fitting method is recommended among the three methods, because more comprehensive fringe information is taken into account to derive the neutral winds by this method.

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    Characterization of Mesospheric Inversion Layer with Rayleigh Lidar Data over Golmud
    QIAO Shuai, PAN Weilin, BAN Chao, CHEN Lei, YU Ting
    2019, 39 (1):  84-92.  doi: 10.11728/cjss2019.01.084
    Abstract ( 436 )   PDF (1578KB) ( 328 )   Save

    Based on the measurements of MARMOT (Middle Atmosphere Remote Mobile Observatory in Tibet) lidar located in Golmud, Qinghai (36.25°N, 94.54°E) from July to December 2014, Mesospheric Inversion Layer (MIL) over Golmud area has been analyzed. The average occurrence frequency of MIL over Golmud is 53.8% during this period. The occurrence frequency is highest and can be up to 76% in winter (December), is around 60% in autumn equinox, and is as low as 29% in summer (July, August). The amplitude of temperature inversion is within 5~20K, and the average value is 15.9K. The mean bottom altitude of MIL is 75.1km. The bottom altitude is higher and mainly from 77 to 84km in autumn. It is lower in winter and summer, and mainly from 64 to 74km. The mean width of MIL is 8.7km, and it increases from summer to winter.

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    Sensitivity Study of Viewing Path and Spectral Resolution on Absorbing Aerosol Index
    ZHANG Zhuo, WANG Yongmei, WANG Weihe, WANG Houmao
    2019, 39 (1):  93-99.  doi: 10.11728/cjss2019.01.093
    Abstract ( 461 )   PDF (2254KB) ( 367 )   Save

    Absorbing Aerosol Index (AAI) has a broad application in pollution monitoring. AAI is influenced by many factors in atmosphere, such as altitude of boundary layer, height of cloud, relative humidity, as well as factors from instrumental properties and geometric observation view angles. The atmospheric radiance transfer model MODTRAN was used to simulate the effects of the streams used in the DISORT multiple scattering calculation in radiance transfer equation and view angle of instrument on the biases of AAI derivation. The results indicate that 8 Streams is the best choice in radiative transfer simulation of aerosol scattering, both in accuracy and computational efficiency. AAI varies similarly with the view angle for different aerosol thickness and types:When Relative Azimuth Angle <120°, the bias of AAI is largest when both the Solar Zenith Angle and Satellite Viewing Angle are between 40° and 60°; When Relative Azimuth Angle <180° and >120°, the bias of AAI is relatively small. Besides, spectral resolution has no significant influence on AAI retrieval results.

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    Design and Experimental Validation of Hindlimb Unloading Rat Suspension Device with Adjustable Body Position
    WANG Min, WANG Shouhui, YANG Xiao, HUANG Yunfei, SUN Lianwen, FAN Yubo
    2019, 39 (1):  100-104.  doi: 10.11728/cjss2019.01.100
    Abstract ( 453 )   PDF (2157KB) ( 348 )   Save

    The rat tail-suspension model was improved in this paper to develop a new type of adjustable body position hindlimb unloading suspension device for rats, which was used to investigate the effect of changes in body fluid distribution under simulated microgravity on bone metabolism in rats. 36 Sprague-Dawley rats were randomly divided into four groups:Control (CON) group, Head-Down-Tilt (HDT) group, Head-Horizontal (HH) group and Head-Up-Tilt (HUT) group. 21 days later, rats were detected for Bone Mineral Density (BMD) with DXA. Severe bone loss occurred in all three groups of rats under the simulated microgravity effect, and the hindlimb BMD of HH and HUT groups significantly increased compared with HDT group. The experimental results show that the changes in body fluid distribution may play an important role on the bone loss caused by simulated microgravity effect, and the new rat hindlimb unloading suspension device can adjust the body position (body fluid) of rats for simulated microgravity effect study.

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    Highly Monochromatic Soft X-ray Beam Source Design
    WEI Fei, GUO Yihong, LENG Shuang, WEI Lai, CAO Leifeng
    2019, 39 (1):  105-110.  doi: 10.11728/cjss2019.01.105
    Abstract ( 586 )   PDF (3630KB) ( 306 )   Save

    The soft X-ray radiation in the range from 100eV to 1keV consists of rich significant emission lines and the blackbody continuum. It is commonly used in X-ray instruments for space scientific missions, and the instruments should be well calibrated for spectral response before the flight. Because of the obvious spectra contamination from higher orders of diffraction, X-ray source used traditional gratings is difficult to get highly monochromatic X-ray beam. A new monochromator based on single-order diffraction grating is designed in patterns of zigzag or photon sieves, which has excellent diffraction characteristics of suppressing all higher orders of diffraction from shorter wavelength. The monochromator can keep the percent of the higher order contamination below 0.3%. The results can bring great advantages in preflight calibration of X-ray instruments for space science purposes.

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    Space Environment Data Transfer System Based on BBR Congestion Control Algorithm
    LIU Pan, CAI Yanxia, LU Guorui
    2019, 39 (1):  111-117.  doi: 10.11728/cjss2019.01.111
    Abstract ( 727 )   PDF (1763KB) ( 343 )   Save

    Space environment data transfer system needs to transfer massive space environment data from the ground monitoring station to the data center through Wide-Area Network (WAN). High loss rate and large delay of WAN influence the normal operation of the space environment data transfer system. In this paper, TCP congestion control mechanism is studied and the BBR congestion control algorithm is used to solve the problems of space environment data transmission. Aiming at the requirements of space environment data transmission, a workflow model of space environment data transfer is designed using Petri-net, and a space environment data transfer system based on BBR congestion control algorithm is established. Finally, it is proved by the experiments that the system is applicable to space environment data transfer on WAN.

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    Evaluation on UERE and Positioning Accuracy of BDS
    LIU Ruihua, WANG Ying, WANG Jian
    2019, 39 (1):  118-128.  doi: 10.11728/cjss2019.01.118
    Abstract ( 950 )   PDF (3759KB) ( 936 )   Save

    User Ranging Error (URE) and User Equipment Error (UEE) are the main factors affecting the positioning accuracy. Civil aviation is the high-end user of BeiDou Navigation Satellite System (BDS). It is necessary to monitor the coverage and service performance of BDS at civil aviation airports. Based on the measured data of BDS at four civil aviation airport observatories, this paper introduces the satellites visibility of each airport, URE solution method, ionospheric delay correction model, tropospheric delay correction model and the evaluation of positioning accuracy. The results show that the number of visible satellites is from 6 to 14, which meets the positioning requirements. At 95% confidence level, the ionospheric delay is better than 7.50m, the tropospheric delay is better than 13.28m, and the URE values of Geostationary Earth Orbit (GEO) satellites, Inclined Geosynchronous Orbit (IGSO) satellites and Medium Earth Orbit (MEO) satellites are better than 2.36m, 1.72m and 2.59m respectively, which meet the requirements of Beidou open service performance specifications. At 95% confidence level, the positioning accuracy is better than 3.63m in the horizontal direction and better than 6.98m in the vertical direction. The coverage and service performance of BDS at the civil airport monitoring stations are good.

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    Mission Planning for Small Satellite Constellations Based on Improved Genetic Algorithm
    HAN Chuanqi, LIU Yurong, LI Hu
    2019, 39 (1):  129-134.  doi: 10.11728/cjss2019.01.129
    Abstract ( 684 )   PDF (962KB) ( 307 )   Save

    Based on operational features of small satellite constellation, a multi-task mission planning problem model for small satellite constellation is established, and a multi-index optimization function based on imaging task period and equilibration is proposed. Furthermore, an improved genetic algorithm involving strategies of random allocation of resources as well as elite population reservation is applied to the established model. The algorithm improves the efficiency of related solution and guarantees the convergence of the final result. The simulation result shows that the improved genetic algorithm is applicable and effective to the specific needs of mission planning problem for small satellite constellation.

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