2010 Vol. 30, No. 2

Display Method:
Application of Solar Photospheric Magnetic Field Properties in SPE Short-term Forecast
Cui Yanmei, Liu Siqing, Wang Huaning
2010, 30(2): 97-104. doi: 10.11728/cjss2010.02.097
Abstract(2540) PDF 928KB(1237)
Abstract:
Solar Proton Events (SPE) are one kind of the major solar energy release phenomena. The released energies are well known from the magnetic energy. Lots of observations and studies have suggested that solar flares and CME (Coronal Mass Eruptions) are closely correlated to the complexity and non-potentiality of solar magnetic fields. Applying SOHO/MDI full-disk photospheric magnetograms, three magnetic physical properties (the maximum horizontal gradient of longitudinal magnetic field Bz, the length of neutral line with strong gradients L, the number of singular points η) are calculated, which describes the complexity and non-potentiality of solar magnetic fields. In order to verify that solar photospheric magnetic properties are available at forecasting SPE, a simple SPE forecast model that can forecast whether SPE will happen or not in the future 24 hours is set up, which is based on the three physical properties with BP (Back Propagation) neural network. In the consecutive tests for the 2002 and 2003 year samples, the model has very high accuracy rates (90 % for 2002 and 87.54 % for 2003, respectively) and the rather high SPE probabilities of detection (60 % for 2002 and 75 % for 2003, respectively), which supported that solar photospheric magnetic properties are very available in the SPE forecast models.
Predicting the Shock Arrival Time Using 1D-MHD CE/SE Solar Wind Model
Zhang Ying, Feng Xueshang, Yang Liping
2010, 30(2): 105-112. doi: 10.11728/cjss2010.02.105
Abstract(2393) PDF 658KB(1173)
Abstract:
A 1D-MHD shock propagation model (1D-MHD (CE/SE) model) is established to predict the arrival time of interplanetary shocks at 1AU, using the space-time Conservation Element and Solution Element (CE/SE) method. Applying this model to 137 solar events during the period of February 1997 to August 2002, it is found that our model could be practically equivalent to the STOA, ISPM, HAFv.2 and SPM models in forecasting the shock arrival time. The absolute error in the transit time from 1D-MHD (CE/SE) model is not larger than those of the other four models for the same sample events. Also, the prediction test shows that the relative error of our model is ≤10% for 25.6% of all events, ≤30% for 69.3%, and ≤50% for 87.6%, which is comparable to the relative errors of the other models. These results might demonstrate a potential capability of our model in terms of real-time forecasting.
Compression Effects of Interplanetary Shock to the Magnetosphere
Yao Li, Liu Zhenxing, Zuo Pingbing, Zhang Lingqian, Duan Suping
2010, 30(2): 113-120. doi: 10.11728/cjss2010.02.113
Abstract(2423) PDF 648KB(1494)
Abstract:
On November 9, 2004, the WIND spacecraft detected a typical interplanetary shock. Before the shock, there is a sustaining weak southward magnetic field lasting about 50 min. Across the shock front, the magnetic field turns northward, and the solar wind dynamic pressure is abruptly enhanced, i.e., the shock is a strong Dynamic Pressure Pulse (DPP). The magnetosphere is compressed to a rather small region upon the impact of the DPP. During the impingement of the shock, the magnetospheric compression causes two-mode disturbances of the energetic particle at the geosynchronous orbit, i.e., particle flux enhancement due to the compression near dawn and dusk and dispersionless particle injection similar to substorm. The disturbances propagate from the dayside to the nightside. The energetic particle fluxes on the dayside first increase, and then after about 1 min, the particle fluxes near dawn and dusk on the nightside begin to increase. Finally, dispersionless particle injection is seen near the midnight. Furthermore, near the noon the responses of electron are prior to those of proton. Contrarily, near the midnight the responses of proton are prior to those of electron. By using GOES-10 and GOES-12 observations on two sides of the noon, it is found that the magnetic field on the dawn-noon sector is simply compressed, while for the magnetic field on the noon-dusk sector, Bx and Bz component decreases, but By component notably increases. The TC-1 spacecraft located at near-Earth low-latitude lobe region observes the shock-induced lobe SI phenomena.
Plasma Diffusive Flows in the Topside Ionosphere From Radio Occultation Measurements by COSMIC
Chen Guangming, Xu Jiyao, Wang Wenbin, Lei Jiuhou, Deng Yue
2010, 30(2): 121-131. doi: 10.11728/cjss2010.02.121
Abstract(2881) PDF 857KB(1125)
Abstract:
O+ field-aligned diffusive velocities and fluxes in the topside ionosphere have been calculated from electron density profiles retrieved from COSMIC radio occultation measurements. The diffusive velocities and fluxes from October 2006 to October 2007 at low-latitude and mid-latitude have been statistically analyzed. The results show that daytime diffusive fluxes changed gradually from downward to upward as altitude increased. The transition height is below hmF2+80 km. The largest values of the upward diffusive fluxes and velocities during the daytime occur at geomagnetic latitudes from 10º to 20º above hmF2+80 km, whereas during the nighttime the maximum downward fluxes occur at geomagnetic latitudes from 30º to 40º. Diffusive fluxes are roughly symmetric around the magnetic equator during equinoxes. But they are asymmetric during solstices, the winter hemisphere has smaller fluxes than the summer hemisphere does. In addition, the diurnal variations have latitudinal dependences.
Study on the Adaptability of the Empirical Storm-time Ionospheric Correction Model STORM in China Region
Wang Shikai, Liu Wen, Lu Zhuanxia, Guo Yanbo, Kong Qingyan, Feng Jing
2010, 30(2): 132-140. doi: 10.11728/cjss2010.02.132
Abstract(2710) PDF 637KB(1348)
Abstract:
Based on the ionospheric f0F2 data from 9 ionosonde stations in China region during a solar activity cycle from 1976 to 1987, the level and the distribution characteristic of the ionospheric storms along seasonal bins and geomagnetic latitudes are statistically investigated. It is found that the small and medium level storms occur more frequently in spring and autumn and the frequencies in different seasonal bins have relationship with the geomagnetic latitudes. A comparison between the storm-time predicted f0F2 values and the monthly median ones shows that the median model can be improved effectively by the STORM model except in winter. It is important of adding Chinese storm-time data and enhancing the prediction accuracy in winter to improve the STORM model. And developing an appropriate storm-time index to predict f0F2 is a key point in the future.
Preliminary Analysis of Ionospheric Scintillations Over Guangzhou Region of China
Wang Siyu, Wang Jinsong, Yu Tao, Shan Haibin, Zhang Xiaoxin
2010, 30(2): 141-147. doi: 10.11728/cjss2010.02.141
Abstract(2702) PDF 783KB(1563)
Abstract:
Ionospheric scintillation is a kind of rapid variation resulting from ionospheric irregularities. The scintillations may cause problems such as signal power fading, phase cycle slips, receiver loss of lock, etc., and degrade the quality of satellite navigation systems. Being concerned about these effects, ionospheric scintillations observed at Guangzhou station (23º8' N, 113º17' E) during April to September, 2007 and January to September, 2008 are analyzed in this paper. The results show that there are more ionospheric scintillations over Guangzhou region during geomagnetic quiet and low solar activity periods. The scintillations with S4>0.2 have high and stable occurrence rate in summer, and show no obvious daily variation. Most of them are weak scintillations, i.e., 0.2
Application of the Ensemble Kalman Filter in Short-term Ionospheric Forecast
Chen Chun, Wu Zhensen, Sun Shuji, Ding Zonghua, Ban Panpan, Zhao Zhenwei
2010, 30(2): 148-153. doi: 10.11728/cjss2010.02.148
Abstract(2294) PDF 525KB(1046)
Abstract:
The short-term ionospheric forecast mainly denotes a prediction from hours to days in advance on time scale. This task needs a nonlinear recursion between the training data and the target one picked from the measurements, even by using complicated mathematic operations. Recently, an optimized arithmetic in data recursions named as Ensemble Kalman Filter (EnKF) has been widely used in temperature and rainfall predictions and even in ionospheric data assimilations. In this paper an optimizing method for short-term ionospheric f0F2 forecast was provided based on the Ensemble Kalman Filter technique. Firstly, the hourly f0F2 values with 1~24 hour in advance were forecasted by the neural network method. Then the forecasted values by the neural network were adjusted and optimized by introducing the Ensemble Kalman Filter after taking into account of the anterior forecast errors and the trend of f0F2 variations. The forecasted errors are binned with seasons and stations and compared with those of purely neural network and International Reference Ionosphere (IRI) to validate this method. The results show that the forecasting performance by the optimizing model is superior to that by the purely neural network and IRI. This indicated that the Ensemble Kalman Filter technique could be an efficient tool in ionospheric short-term forecast. Furthermore, this optimizing method can also be applied to the short-term forecasting of other ionospheric parameters.
Research of the Optical Effects of Space Weathering on Lunar Regolith Based on the Nonlinear Mixing Model
Wu Yunzhao, Zheng Yongchun, Zou Yongliao, Xie Zhidong, Xu Xisheng
2010, 30(2): 154-159. doi: 10.11728/cjss2010.02.154
Abstract(2494) PDF 575KB(1372)
Abstract:
The reflectance spectrum of lunar soil is mainly dominated by its composition and the degree of exposure to space weathering processes such as micrometeorite bombardment and solar wind implantation. The spectral alteration effects of space weathering should be removed for accurately investigating the composition of the lunar surface using remote sensing data. It can contribute to develop the method for decoupling the spectral effects of composition and maturity to improve the inversion accuracy by exploring the optical effects of space weathering on lunar regolith. Because unweathered soil is hard to acquire, it's unable to compare the spectra between the weathered and unweathered soil directly. This paper provided a simple way to investigate the optical effects of space weathering. First, the mixed spectra is acquired according to the mineral contents and spectra measured from the lunar soil using the Hapke model. Then the modeled spectra of lunar soil were compared with the real spectra measured by Brown University. Investigation results showed that the space weathering can reduce the overall reflectance of lunar soil, and the shorter waveband the greater reducing; that it can increase the continuum slope to the spectrum, which makes the spectra redder; and it can also reduce the absorption depth and spectral contrast, and the absorption peak near 2.0μm was reduced more than that near 1.0μm. These factors should be taken into consideration when the element contents are retrieved using remote sensing technology.
Research on Control and Experiment of a New Lunar Rover
Ge Weiping, Liu Tun, Yuan Laohu, Zhao Zhiping
2010, 30(2): 160-164. doi: 10.11728/cjss2010.02.160
Abstract(2067) PDF 644KB(1339)
Abstract:
Because of the complexity of the lunar environment, the lunar rover, as a complex multi-body system, has many characteristics in its dynamics behavior and its control. The analysis is more difficult than that of simple system. The mathematical models of lunar rover control, such as dynamics, motion constraints and kinematics, are presented in this paper. The harmonious control is explained by the sample of running across a ravine. For imitation of the lunar gravitational circumstances, a single wheel test device based on gas lubrication was designed. The range of the kinematic and dynamic parameters of each wheel can be determined by that device.
Fluid Loops in General-purpose Space Science Experimental Platform
He Chongchao, Zhang Hanxun
2010, 30(2): 165-169. doi: 10.11728/cjss2010.02.165
Abstract(2087) PDF 831KB(1168)
Abstract:
Space Science Experimental Platform (SSEP) is a multi-function experimental platform being developed as an alternative for traditional single-function experimental apparatus. This paper introduces the designs of heat transfer fluid loops in SSEP, and related design methods for some major equipment, including Avionics Air Assembly (AAA) fan, gas-liquid heat exchanger and cold plates. Suggestions for working fluid selection are also listed with the considerations of heat transfer efficiency and system safety. Preliminary analysis results, as well as the successful application of such designs in similar platforms developed by ESA and NASA, proved that fluid loop heat transfer technology, combined with complementary active and passive thermal control measures, can maintain the multi-function experimental platform and its payloads within their required temperature limits.
Experimental Research on SET Effects of Operational Amplifier
Feng Guoqiang, Hu Yonggui, Wang Jianan, Huang Jianguo, Ma Yingqi, Han Jianwei, Zhang Zhenlong
2010, 30(2): 170-175. doi: 10.11728/cjss2010.02.170
Abstract(2586) PDF 536KB(1074)
Abstract:
In recent years, the Single Event Transient (SET) has gradually come into focus in the field of Single Event Effect (SEE) research. The SET effects of operational amplifier SF3503, which is designed in the applications of inverting amplifier and voltage comparator, have been investigated by pulsed laser test facility. The equivalent Linear Energy Transfer (LET) has been calculated with the pulsed laser and device parameters, including pulsed laser wavelength, energy and dielectric depth in device. The identification of sensitive nodes, LET threshold and SET pulse shape characteristics has been tested. While all the sensitive nodes are included in the input stage and amplified stage, LET threshold is no more than 1.2 MeV•cm2•mg-1, the amplitude of 27 V and duration of 51μs have been achieved in the voltage comparator. Positive, negative and dual polar pulses were observed in the experiment. The transistor Q16 of amplified stage has been examined as the most susceptible node in the circuit. For the vulnerable SET effects of the SF3503, the device is not qualified for application in the space mission directly.
Design and Implementation of a High Speed Modulation System for Space Applications
Lin Miao, Wang Pinglian, Zhang Lei
2010, 30(2): 176-179. doi: 10.11728/cjss2010.02.176
Abstract(1806) PDF 458KB(1122)
Abstract:
To meet the requirements of high speed data transmission, multi-level modulation and the system flexibility in space applications, a modulation system design scheme was introduced, which has adopted the new techniques of the FPGA and DAC based communication system, and can be used for high speed data transmission with QPSK, 8 PSK, QAM or other kinds of digital modulation. The difficulties such as the high speed based-band signal conversion, wide-band modulation, carrier suppression, high frequency and high precision clock generation in the design and implementation of this modulation system are analyzed, and the solutions are also given. The test result shows that this modulation system can satisfy the performance requirements for most space applications. When the carrier frequency is 2 GHz, the transfer data rate of this modulation system with 8PSK modulation is up to 750 Mbit/s, while the EVM (Error Vector Magnitude) of the modulated signal is only 3.3 %.
Research of Software Updating for Micro-satellite in the Orbit Based on Dynamic Link With Macros
Li Leixia, Wang Yu, Lin Baojun, Zhang Shancong
2010, 30(2): 180-184. doi: 10.11728/cjss2010.02.180
Abstract(1894) PDF 550KB(1132)
Abstract:
To repair the bug of on-board software design, consummate the software application and increase the satellite performance in use, satellite designers begin to pay attention to uploading satellite software in orbit. Modular design method based on on-board computer architecture has been studied to improve the efficiency of software updating. Dynamic link technology between modules, the feasibility and security during updating are key points of this method. In this paper, a specific uploading method has been put forward based on a micro-satellite. Firstly, the on-board software was designed in modules and the dynamic links between modules were realized with macro instructions. Then, by validating the module information structure, higher reliability and security have been achieved. Lastly, validation experiments and analyses have been conducted.
Development of Azolla Wet Culture Device for Supplying O2
Chen Min, Liu Rundong, Yang Youquan, Deng Sufang, Zhan Jie, Huang Yibin
2010, 30(2): 185-192. doi: 10.11728/cjss2010.02.185
Abstract(2630) PDF 762KB(1260)
Abstract:
Azolla is an important biological component of the Controlled Ecological Life Support System (CELSS), because it can supply O2 and absorb CO2 from the environment, and can be used as a fresh vegetable by the astronauts. Developing Azolla wet culture device for supplying O2 to set up non-living components on the ground aims to meet the needs of simulation research. The structure characteristics and working principles of the device and its key component are introduced in this paper. By structure and function designation of medium in Azolla wet culture plate, infiltration pipeline of capillary action is set inner store and conserve water stroma layer to keep the overall surface of medium wet but no obvious water always, which creates beneficial conditions for rooting and fixing, nutrient absorption, growth and reproduction. The main technical parameters of water pipe line and intermittent circulatory periods of closed Azolla culture medium transmission and distribution system are determined in the hydraulic pressure test. The results of machine output test show that when the interlayer spacing is 125\,mm, Azolla wet culture area of overall unit is 6.3 m2, using ultra-high brightness white LED as artificial light source, Azolla surface light intensity is 6000~6500 lx, the energy consumption is 152Wm2, Azolla yield, the amount of O2-release and CO2-absorption of overall unit will be increased by a wide margin, and every performance index is in accordance with the design requirement.