2012 Vol. 32, No. 6

Display Method:
Global Distribution of Currents in Martian Space
LIU Tongdi, LI Lei, ZHANG Yiteng, XIE Lianghai
2012, 32(6): 765-770. doi: 10.11728/cjss2012.06.765
Abstract(2356) PDF 1032KB(1224)
Abstract:
Based on the MHD model, distribution of the currents in Martian space is calculated. The results show that there are 4 categories of currents, i.e., the bow-shock current, magnetic pileup boundary current, the ionosphere current and the magnetotail current in Martian space. Currents flow on the surface of the bow-shock independently, which direction are perpendicular to the interplanetary magnetic field direction, with the peak current density located around the subsolar point. At dayside, the magnetic pileup boundary current closes through the ionosphere; while at nightside, magnetic pileup boundary current couples with central current sheet in the magnetotail to form a complete circuit. Magnetotail central currents near Mars within 1.2Rm affected greatly by the ionosphere, would be separated for two or more current slices coupling together. The strength of ionosphere current, flowing from south to north, is the biggest in all, more than 100nA·m-2 in average; and the strength at dayside is bigger compared to that of the nightside.
Study for Prediction Method of X-Ray Flare Characteristic Parameters
GUO Ce, XUE Bingsen, LIN Zhaoxiang
2012, 32(6): 771-777. doi: 10.11728/cjss2012.06.771
Abstract(2351) PDF 549KB(1048)
Abstract:
Solar flare is an important space weather event, and prediction for the parameters of it is important to the warning of Sudden Ionospheric Disturbance (SID). It is well known that the revolution of solar soft X-ray flares follows some pattern, especially the long duration ones. Through events analysis, it is found that the early stage of rising phase of the solar flare always indicates the peak flux. After checking the process of recent events, the pattern of flux of flare developing become clear that the rising rate flux decrease continuously until reaching the peak. To simulate this process, a mixed fitting model was built and the basic idea stands that the time X-ray data is fed into the model and relative prediction result could be derived from each group of data. When the difference between adjacent two is within point scale, the fitting parameter is then determined and stored in the model. The prediction of the flare will be made with these parameters. The evaluation of the model was done with the big flare in 23rd solar cycle and the result is acceptable with the error less than 20% and the peak time could also be well predicted. The decreasing phase of the flare was also investigated and the result showed that most of the flares go down following a minus e-fold pattern. Although the appearance of each flare is different, its decreasing curve could be simulated with the data after peak time. The fitting parameters would be derived through 10 data points. The result of the fitting model indicates that the ending time of flare could be well predicted. Judging from the forecast results with historic data, the prediction method has a certain validity and practicability. The dynamic fitting model was also tested with newly occurred flare. The size and peak time were well predicted, which proved that this method could be applied to prediction practically.
Characteristics of Reconnection Diffusion Region in the Solar Wind
XU Xiaojun, WEI Fengsi, FENG Xueshang
2012, 32(6): 778-784. doi: 10.11728/cjss2012.06.778
Abstract(2399) PDF 921KB(1053)
Abstract:
A Petschek-like reconnection exhaust of extremely low plasma density was detected by ACE and WIND on 6 January 2007 near 1AU in the solar wind. The exhaust is characterized by an apparent Hall bipolar magnetic field, ion and electron density depletion layers and pitch angle distribution of low energy electrons anti-parallel to the direction of Hall current. Such features indicate a possible reconnection ion diffusion region in the solar wind. To the best of our knowledge, this is the first time to report direct detections of ion diffusion region associated with solar wind reconnection exhaust. Observations show that the associated reconnection is quasi-steady, almost anti-parallel merging (no guide field) and fast with a dimensionless reconnection rate of about 2%. Meanwhile, the diffusion region is bounded by a pair of slow-mode waves and the spatial width is up to 80 ion inertial lengths, performing large-scale characteristics of reconnection for large systems.
2.5D AMR MHD Magnetic Reconnection Model
ZHANG Shaohua, FENG Xueshang, YANG Liping
2012, 32(6): 785-792. doi: 10.11728/cjss2012.06.785
Abstract(2588) PDF 823KB(933)
Abstract:
Magnetic reconnection is one of the hot topics in space physics. The magnetic Lundquist number can influence the magnetic reconnection process drastically. Magnetic Lundquist number is always very large in many real physical environments, for example, higher than 104 in interplanetary space and solar corona. Magnetic reconnection with enormously large Lundquist number behaves many new characteristics, while magnetic reconnection simulation needs very high grid resolution, or it can't resolve the thin current sheets formed in the magnetic reconnection. With the help of the Adaptive Mesh Refinement (AMR) package named PARAMESH, AMR technique was introduced into magnetic reconnection simulations and a two and half dimensional (2.5D) AMR magnetic reconnection model was developed. The dynamic reconnection process with different magnetic Lundquist numbers was studied. The results showed that this model can automatically capture the near-singular current sheets with the development of the magnetic reconnection and the slow-mode shock structures formed in the magnetic reconnection process with high magnetic Lundquist number provide a possible way for fast magnetic energy conversion.
Variation of the Bz Component of Magnetic Field During the Front of Bursty Bulk Flows
SHENG Cheng, FU Suiyan, ZHENG Hao, BAI Xi, YANG Biao, WANG Yongfu
2012, 32(6): 793-803. doi: 10.11728/cjss2012.06.793
Abstract(2191) PDF 1008KB(1041)
Abstract:
Bursty Bulk Flows (BBFs) play an important role in the magnetotail activites. The formation mechanism of BBFs and the interaction between BBFs and the ambient plasma have become important research subjects recently. Based on the observations made by Cluster during the periods from July to October 2001 and 2002, the variations of magnetic field during the passage of BBFs are statistically analyzed. Superposed epoch analyses show that there is a sharp change in the Bz component as the bulk speed of the flow begins to increase at the front of BBFs: a sharp increase preceded by a transient decrease. This signature in Bz component was found in most of the BBFs events observed by Cluster, which is generally agreed with the result reported based on Geotail observations. However, the change of Bz component is not always symmetry, and the decease of Bz is usually not strong enough to lead to a negative value. This implied that magnetic structure does not always occur together with BBFs. The interaction between BBFs and ambient plasma is responsible for the change in Bz. After the dipolarization front is formed, the diamagnetic effect due to the hot ions bouncing back from the boundary might contribute to the decrease in Bz. The pile-up of the magnetic flux carried by BBFs may be the reason for the increase.
Effect of Solar Cycle Activity on High Energy Proton of Inner Radiation Belt in the Low Altitude Region
SHI Liqin, LIN Ruilin, LIU Siqing, ZHENG Huinan
2012, 32(6): 804-811. doi: 10.11728/cjss2012.06.804
Abstract(2505) PDF 702KB(1179)
Abstract:
The NOAA-15 high energy proton observation from 1998 to 2011 is used to analyze the effect of solar cycle activity on high energy proton flux. The statistic research indicates that there is an inverse correlative relationship between the proton flux in inner radiation belt and solar activity. This anti-correlation is related to geomagnetic coordinates L and B, and more significant with the increasing of L and decreasing of B. There is also a phase lag between the solar activity and the proton flux. This hysteresis effect is more obvious in the region with smaller L or larger B. The lag can reach one year in some regions. This hysteresis effect means it takes a long time to reach the dynamic balance between the source and the loss for the proton of inner radiation belt in the low altitude region. The unbalance between the source and loss is the reason why the intensity of proton flux at the same solar activity is different. The comparison with the result of AP8 model indicates the energetic proton flux from AP8 is higher than the satellite's observation in the region with large B, which suggests that the AP8 model may overstate the proton flux enhancement at inner radiation belt in the low altitude region if only the long-term variation of magnetic field is considered.
Impact of Geomagnetic Storms on L-band Ionospheric Scintillation Over Equatorial Region
YANG Shenggao, FANG Hanxian, LI Gang, NIU Jun, WANG Kai
2012, 32(6): 812-817. doi: 10.11728/cjss2012.06.812
Abstract(2703) PDF 548KB(1351)
Abstract:
Using the observation data at Vanimo station, the amplitude scintillation intensity and the occurrence rate were analyzed during the two classic different strong magnetic storms. Mechanism of the magnetic storm influence on the scintillation was discussed preliminarily by Rayleigh-Taylor instability linear theory. The results show that the magnetic storm could either triggering or inhibiting the scintillation, which relates to the season and the local time of the different period of the magnetic storm. If the magnetic storm main phase occurs from midnight to dawn, the scintillation may be triggered by the eastern ward electrical field, and if the magnetic storm recovery phase takes place during the pre-midnight, it may be inhibited by the western ward electrical field. The electrical field variation during the magnetic storms is possibly the main factor that influence the scintillation, but it needs further study to prove.
Heating of Lower Ionosphere by Powerful HF Radio Wave
WANG Sicheng, FANG Hanxian, YANG Shenggao, WENG Libin
2012, 32(6): 818-823. doi: 10.11728/cjss2012.06.818
Abstract(2281) PDF 539KB(1436)
Abstract:
The ionospheric heating by powerful HF radio wave can excite the disturbance of temperature, density and other parameters of ionospheric plasma. Based on Ohmic theory, the effect of high power radio wave on the lower ionosphere is studied, and the following conclusions can be drawn. Firstly, D region is the main absorption area of the radio wave, and the intensity of absorption decreases with the increase of radio wave frequency. When radio frequency is 6MHz (effective radio power is 200MW), the electron temperature increase can be up to nearly 520K, and electron density increase can reach about 7300cm-3. Secondly, the disturbance of electron temperature and density tend to be saturated after continuous heating. The time that the electron temperature needs to be saturated is of a scale of μs, while that of the electron density is ms. When stop heating, the electron temperature and density come back to the normal conditions quickly. Thirdly, the higher radio power is, the larger disturbance of electron temperature and density are caused, and the longer saturation time is needed. The saturation time at nighttime is longer than that at daytime under the same heating conditions.
Spectra of the OH Airglow Perturbation on 5 Januray 2009 at Langfang
TU Cui, HU Xiong
2012, 32(6): 824-828. doi: 10.11728/cjss2012.06.824
Abstract(2075) PDF 708KB(1148)
Abstract:
It is necessary to observe and analyze the characters of gravity waves to study their effect to upper and middle atmosphere. The first imaging observation experiment of the atmospheric gravity waves in the mesopause region in China with the all-sky OH band airglow CCD imager is made on 5 January 2009, at Hancun (39.4°N, 116.6°E), Langfang, Hebei. Based on the nearly 4-hour data, we obtained the specta of OH airglow perturbation during this time period, with a horizontal range of about 185 km centered around the observatory (at Hancun, Langfang). The unambiguous power spectrum and angular spectrum method is approved by simulation. The parameters of three quasi-monochromatic gravity waves analyzed before agree with the unambiguous power spectrum. The unambiguous power spectrum and angular spectrum reveal the distribution of wavelengths and propagation directions of the gravity waves during the 4 hours: the lower limit of wavelength is short; the gravity waves propagate more west than in the east. Compared with the results in other two papers, the directions are different in different sites even in the same season and similar altitudes, which may be related with the different sources of the gravity waves.
Variation of the Upper Atmospheric Density During the Quiet Period of Solar and Geomagnetic Activity (2007?2009)
LI Yongping, ZHU Guangwu, QIN Guotai
2012, 32(6): 829-833. doi: 10.11728/cjss2012.06.829
Abstract(2210) PDF 411KB(1234)
Abstract:
The period of low solar activity between solar cycle 23 and 24 last a long time, having low F10.7 and long-term sunspot number record. So it is the time to study the change of upper atmospheric density in this quiet solar and geomagnetic activity conditions, especially for study of the response of upper atmosphere to variations in small geomagnetic disturbance and low solar activity. Atmospheric density detector mounted on the satellite near 650km aims at getting measurement data with the change of geomagnetic and solar flux variability, whose data are available ranging from 2007 to 2009, the results are concluded as follows. Upper atmospheric density obviously responses to the F10.7 variation in condition of low solar activity. When F10.7 decreases from 70 to 65, daily atmospheric density decreases obviously for 4~5 times, which is much larger than the decrease in the model. Upper atmospheric density also obviously responses to the small geomagnetic disturbance. Atmospheric density is increased strongly by 80%~160% when the sum of Kp increases from 23 to 30.
Design of Data Acquisition and Processing Unit for Complex Detector in the Ionosphere
LIU Wei, ZENG Li, SONG Jingxing
2012, 32(6): 834-840. doi: 10.11728/cjss2012.06.834
Abstract(2433) PDF 632KB(1140)
Abstract:
Complex Detector in the Ionosphere (CDI), designed for fast responsive spacecraft platform, is a novel conceptual payload instrument for in-situ plasma and partially ionized gases complex measurement in the ionosphere. CDI is an integrated miniature of conventional planar Langmuir probe, retarding potential analyzer and ion trap mass analyzer. In this article, based on USB2.0 and FPGA (Field-Programmable Gate Array techniques using Commercial-Off-The-Shelf (COTS) parts with highly integration level, a multi-channel Data Acquisition and Processing Unit (DPAU for CDI instrument is designed. The DAPU system and hardware design are both introduced. In addition, analysis on logic resource of FPGA and simulation on reading and writing time sequence are also introduced in the article.
Research of a Mass Flow Controller for Microgravity Environment
LI Ming, YU Qiang, ZHAI Guangjie, SUN Zhibin
2012, 32(6): 841-845. doi: 10.11728/cjss2012.06.841
Abstract(2040) PDF 509KB(1013)
Abstract:
A highly reliable method of mass-flow controller design is proposed. The controller is composed of 4 parts, i.e., control circuit, Micro-Electro-Mechanical Systems (MEMS), needle valve and step motor. Different gas flow meters and control valves are compared, and then MEMS and needle valve are selected. The MEMS, as an integrated chip, has better vibration resistance and smaller size, and its working temperature can meet the space experimental requirements. The output voltage from MEMS is amplified by subtraction amplifier circuit, through A/D sampling and software filtering, and an output voltage value is obtained, which denotes the actual gas flow. By comparing the sampling value and the set value of gas mass flow, PID algorithm is used to count step motor control parameters, including the amount of pulse and the direction. Then the needle valve adjusts gas mass flow by step motor to reach the set value of gas mass flow. The experimental results are given by using this gas mass flow controller for oxygen flow control. The whole system can neatly adjust gas flow in demand and reach the experimental requirements for space equipment. It lays the foundation of using mass flow controller in China's future space experiment.
Research of Wireless Sensor Networks for Intra- Spacecraft Environmental Monitoring
ZHOU Li, CAO Song, AN Junshe
2012, 32(6): 846-854. doi: 10.11728/cjss2012.06.846
Abstract(2876) PDF 816KB(1400)
Abstract:
Wireless interface service is now one of the most interesting and newest avionics technologies. The wireless technology will be used widely in space exploration in the future. Considering the characters of the intra-spacecraft environmental monitoring, a system scheme based on wireless sensor networks is designed, in order to decrease the power consumption as well as the spacecraft mass and volume. A low power RF chip and the ZigBee protocol stack Z-Stack of TI are used to design a demonstrator. The network structure and the sensor node architecture, including its hardware and software design, are described. The demonstrator can monitor the environmental parameters of the intra-spacecraft and its instruments, e.g., temperature, humidity, the instruments' voltage and current. Experiments have been carried out. The results indicate that the sensor nodes' power consumption is extremely low, the mesh network architecture is robust and flexible, and the use of ZigBee Pro for WSN can achieve stable transmission of data between multiple terminals.
Parameter Identification and Improvement in Empirical Model of Flywheel Disturbance
ZHU Min, ZHANG Yonghe, YIN Zengshan
2012, 32(6): 855-861. doi: 10.11728/cjss2012.06.855
Abstract(2040) PDF 576KB(1052)
Abstract:
It is a basic and key technology for high stability and high resolution optical satellite to identify the parameter of flywheel disturbance model accurately. There are two main disturbance models of the flywheel, i.e., empirical model and analytical model. The parameters that need to be identified in empirical model are harmonic numbers and amplitude coefficients. The effects of truncation of the time domain are neglected in traditional parameter identification method when calculating the amplitude coefficients, while the errors of the coefficients are not small sometimes, which can lead to uncertainty to the high frequency jitter response analyses. In order to improve the accuracy and reliability of the disturbance model, this paper presents windowing method and related recovery technique in frequency domain. From the result of simulation, it can be seen that this method improves the accuracy of the parameter significantly.
Numerical Calculation and Research of the Effects of Secondary Emission Characteristics on Surface Charging
ZHANG Jian, XIE Aigen, WANG Ling, WANG Tiebang
2012, 32(6): 862-868. doi: 10.11728/cjss2012.06.862
Abstract(2302) PDF 506KB(968)
Abstract:
Surface charging is a space environment effect. It is one of the major incentives for spacecraft anomalies and failures, which is caused by the space environment. By using more accurate universal formulas for the secondary electron yield from metals and the local current balance model, the charging potentials of shaded-surfaces of a spacecraft are calculated for different surface materials and shapes in MATLAB. According to the results, we draw several curves of the charging potentials and the maximum secondary electron yield. Based on the numerical results, the secondary electron yield and the curves, it can be concluded that spacecraft surface charging have a great relationship with the maximum secondary electron yield, atomic number and the secondary electron yield caused by incident ions. These give certain reference value for the selection and design technique of surface materials.
Properties of New Polyimide Film for Spacecraft
WANG Lei, QING Fengling, FAN Hanlin
2012, 32(6): 869-873. doi: 10.11728/cjss2012.06.869
Abstract(2031) PDF 394KB(1211)
Abstract:
Atomic oxygen is one of the hazard factors for spacecraft in Low Earth Orbit (LEO). Atomic oxygen interacts with thermal control coatings. The interaction is very aggressive toward coatings properties, especially their thermo-optical properties which are the most important for spacecraft thermal control. Depending on the relationship of conformation and performance, new polyimide film was synthesized to improve the atomic oxygen resistance. The results of atomic oxygen with ground simulation test indicate that the second surface mirrors thermal control coating made by the new polyimide film has better atomic oxygen resistance properties than the coating being in use. Environmental adaptability tests such as ultraviolet irradiation test, proton irradiation test, electron irradiation test were made also. The test results show that the second surface mirrors thermal control coating has very good performance.
Study on the Autonomous Celestial Navigation of Near Space Vehicles With Hypersonic Speed Based on Non-Keplerian Orbits
LI Hailin, WU Dewei
2012, 32(6): 874-880. doi: 10.11728/cjss2012.06.874
Abstract(2297) PDF 526KB(2185)
Abstract:
In allusion to the problem that the aircraft autonomous celestial navigation is not suitable for the near space vehicles with hypersonic speed, an approach of the autonomous celestial navigation of near space vehicles with hypersonic speed based on non-Keplerian orbits is studied. Mechanism of the autonomous celestial navigation based on non-Keplerian is analyzed, and the dynamic equations are developed by analyzing the strength of near space vehicles with hypersonic speed. The space motion equation is educed using the vector derivatives rules. States model based on non-Keplerian orbits and measurement model using the concept of stellar horizon atmospheric refraction are designed, and the Kalman filter simulation is adopted. Results show that the autonomous celestial navigation of near space vehicles with hypersonic speed based on non-Keplerian orbits can meet the requirement of high precision for position and velocity, which is important for further research on the near space vehicles with hypersonic speed.
Simulation of Nequick Parameters of Galileo Satellite Navigation System
XIE Jie, ZHANG Bo, HOU Bo, YAO Zhicheng, LIU Guangbin
2012, 32(6): 881-886. doi: 10.11728/cjss2012.06.881
Abstract(3251) PDF 527KB(1336)
Abstract:
The simulation model of Galileo ionospheric parameters based on IGRF is proposed to solve the problem that ionospheric parameters estimation is related to geomagnetic coordinates. Using IGRF, the geomagnetic elements of the geomagnetic field and the Electron Density can be computed at a given location and time, sequentially, the ionospheric parameters of Galileo can be calculated. The simulation results show that the ionospheric delay calculated by this model is consistent with the value observed by IGS, and the precision is higher than those by other models, which proves that the high precision simulation of the Galileo ionospheric parameters is realized.
Directional Detection of the Quasi-inertial Satellite GPS Receiver Antenna Installation Angle
WU Huiying, CHEN Hongyu
2012, 32(6): 887-892. doi: 10.11728/cjss2012.06.887
Abstract(2295) PDF 539KB(1249)
Abstract:
The GPS (Global Positioning System) receiving antenna installation angle on a quasi-inertial orientation of the exploration-satellite is studied. Firstly, according to the mission requirements, the satellite attitude requirements are analyzed. Secondly, theoretical analysis and simulation were conducted according to the attitude requirements of posture on the installation of the GPS receiver antenna installation angle, preferably by the GDOP (Geometric Dilution of Precision) values. Finally, conclusion is drawn based on the simulation results that the GPS receiving antenna axial is near to the ± y axis of body reference frame, viz. the orbital plane normal or negative normal direction.
Research of the Satellite Antenna Alignment Testing
WANG Hongjian, ZHANG Dehai, LIU Heguang, CHEN Xue, YI Min, LIU Guang
2012, 32(6): 893-896. doi: 10.11728/cjss2012.06.893
Abstract(1843) PDF 479KB(961)
Abstract:
The synthesis of the antenna pattern measurement and optics measurement is outlined to test the antenna beam alignment. This paper will discuss the application of alignment techniques and tools in the far-field and near-field test facility. Boresight of the antenna was measured by the standard alignment telescope together with the far field pattern test, while the new method to measure the antenna's beam alignment based on the planar near field method was also proposed. This method used the auto-collimator and porroprism with the antenna near-field planar scan test system. The boresight of Haiyang-2 satellite calibration radiometer antenna measurement results verified the validity and accuracy of this method. Both of these two methods can also be opplied to the common high gain antenna measurement.
A Spatial Redundant Robotic Manipulator’s Chaotic Self-motion
GE Xinfeng, YIN Zhifeng
2012, 32(6): 897-902. doi: 10.11728/cjss2012.06.897
Abstract(2147) PDF 515KB(2254)
Abstract:
The model and kinematics equations of a floating redundant spatial robotic manipulator are established. The Jacobian matrices are analyzed, and the inverse kinematics is obtained. Chaotic motions which existed in the floating spatial redundant robotic manipulator's self-motions are proved by simulation. At last, a spatial 3R redundant robotic manipulator is taken as an example, and the links' self-motion has been studied when the end-effector tracking a plane path repeatedly in its workspace for PD controlling by analysis of direct observation, time history method, phase diagram method, and poincare mapping method. Results show that there exist chaotic motions in the self-motion of the floating spatial redundant robotic manipulator when solving the floating redundant robotic manipulator's inverse kinematics based on pseudo-inverse Jacobian matrix.