空间科学学报

2009 Vol. 29, No. 3

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Feature of the Martian Magnetic Field Structure

ZHANG Yiteng, LI Lei

2009, 29(3): 257-261. doi: 10.11728/cjss2009.03.257

Abstract(3643) PDF 603KB(1680)

Abstract:
Based on a single-fluid MHD model, this paper has studied the global magnetic field structure in the near-Mars space, and investigated the influence of the Martian crustal magnetic fields on the magnetic field structure. Mars bow shock, Magnetic Pileup Region are produced when the solar wind flows over Mars. The interplanetary magnetic field lines are curved and `draping' around the planet. The majority of magnetic field lines bypass over two poles, leaving `V shaped' structure in the wake behind Mars. Near the surface of Mars, the local crustal magnetic fields also have noticeable influence on the magnetic field structure. The crustal magnetic fields at different positions, with different intensities form the dissimilar magnetic filed structure and mini-magnetospheres when interacting with the solar wind. The towed mini-magnetosphere and the mini-magnetosphere with open magnetic lines are illustrated in the paper. The local crustal magnetic fields change the morphology of the magnetic field, and accordingly may play an important role in determining the plasma distribution.

Study on Langmuir Wave Activities Within the Magnetic Cloud Boundary Layers

Zuo Pingbing, Zhu Chunming, Wei Fengsi, Feng Xueshang, Li Huijun

2009, 29(3): 262-267. doi: 10.11728/cjss2009.03.262

Abstract(3595) PDF 805KB(2629)

Abstract:
Two particular types of Langmuir wave activities are found within the Magnetic Cloud Boundary Layers (MCBL): Langmuir wave enhancements in entire region of MCBL compared with the adjacent magnetic cloud body and sheath region for majority MCBL and the rapid Langmuir wave burst phenomena associated with broad-band Doppler shifted ion-coustic wave activities for a few MCBL. On 3 Oct., 2000, WIND detected a typical MCBL inside which rapid Langmuir waves burst was observed. The Langmuir waves burst was right corresponded to the magnetic field minimum within the MCBL. The analysis based on high resolution electron distribution function data indicates that the bump-on-tail instability, resulting from the electron beam with beam velocity vb about7×10^3 km/s, is responsible for the rapid Langmuir waves burst.

Ionospheric Responses to IMF Southward Turnings in Mid- and Low-latitudes

Sun Shuji, Chen Chun, Ding Zonghua, Ban Panpan, Xi Dilong

2009, 29(3): 268-274. doi: 10.11728/cjss2009.03.268

Abstract(2685) PDF 677KB(1160)

Abstract:
Using the historical data from ionosonde stations and satellite, the response of ionospheric f0F2 to major Interplanetary magnetic Field (IMF) southward turnings in mid- and low-latitudes is studied. It shows that the IMF southward turnings can cause disturbing response in the ionosphere, which depends on latitude, season and local time when the turning occurs. In mid-latitude, the ionospheric response to southward turnings in summer and equinox and by night is stronger, which fades out with latitude decreases. During the recovery phase the irregular fluctuation in the ionosphere comes forth. In low-latitude, the disturbance caused by the turnings is strong in summer and equinox and weak in winter, although it tends to be immersing into the background disturbances. It is also found that the maximal negative responses of the ionosphere is well related with the maximal negative Bz after the southward turnings linearly.

Comparison Study of IRI-2007 Spread-F Occurrence Predictions and Observations

Huang Weiquan, Xiao Saiguan, Xiao Zuo, Zhang Donghe, Hao Yongqiang

2009, 29(3): 275-280. doi: 10.11728/cjss2009.03.275

Abstract(4352) PDF 605KB(1085)

Abstract:
Ionospheric spread-F is a frequently-seen ionospheric phenomenon which plays an important role in the study of ionospheric physics. The latest IRI-2007 has extended a new function of spread-F occurrence prediction, which is based on the observational data of some low latitude stations around American sectors. The purpose of this article focuses on the accuracy of the model to see if there is regional restriction by comparing the actual observation data of spread-F occurrence at African sectors with prediction made from this model. The spread-F occurrence prediction model is based on the data of stations in American sector near the equator, while in this article we choose the data of the stations with almost the same latitude in African sector. The results show that there are obvious differences between the observations of these two African station and predictions made by the IRI-2007 model in the annual behavior of average daily occurrence rate, local time variations of annual average values and the trend with solar activity. On the other hand, the observational variations in the American stations of low latitudes and that of IRI-2007 model predictions are fairly in agreement. These results indicate that: (1) the statistical method of IRI-2007 spread-F prediction model based on the Brazilian stations' data is very good and of great reference value because it well reflects the occurrence of Spread-F in American Sector; (2) the equatorial and low latitude ionospheric spread-F phenomena show strong longitudinal effect, and the use of this model in regions other than American sector should be very careful. With different region's observational data, the universal usability of this model could be improved based on the same statistical method used in this model; (3) it provides a tool to study the longitudinal effects of spread-F by comparing the model predicted values and observational values under various conditions.

TEC Compensated Inversion Method of Ionospheric Occultation

Liu Zhaolin, Sun Xuejin, Fu Yang

2009, 29(3): 281-286. doi: 10.11728/cjss2009.03.281

Abstract(2666) PDF 686KB(1269)

Abstract:
A calibrated TEC of Abel inversion method is usually applied in the inversion of ionospheric occultation data, which could cause error for the spherical asymmetry of the real ionosphere. This paper studies a method, TEC compensated inversion method. Combined with background field, this method removes the effect of TEC from the horizontal change of the electron density to improve the applicability of spherical symmetry and inversion accuracy. Then the method is applied in the inversion of simulated data. The result of simulated data inversion validates that TEC compensated inversion method decreases the inversion errors greatly, compared with Abel inversion method. Through the study on background fields obtained by different ways with TEC compensated method, the more close between background and real field, the better inversion result is obtained.

The Ion Distribution Function From Maxwell Molecule Collision Model and Calculations of Incoherent Scatter Spectra

Xue Kun, Guo Lixin, Wu Jian, Xu Bin, Fang Chaofeng

2009, 29(3): 287-295. doi: 10.11728/cjss2009.03.287

Abstract(3026) PDF 719KB(1426)

Abstract:
With regard to anisotropic plasmas, the Maxwell molecule collision model is used to describe ion-neutral collisions of Boltzmann equation. The viscous and heat flow are included in transport equations based on the two-Maxwellian distribution. The expressions of the ion drift velocity, ion parallel and perpendicular temperature, stress tensor and heat flow for parallel and perpendicular energy can be obtained by solving the transport equations. The ion velocity distribution of Maxwell molecule collision model can be obtained using the 16-moment approximation. According to the Sheffield's theories, the incoherent scatter spectra are calculated. In comparison to relaxation collision model, it is reasonable to use the Maxwell molecule collision model to describe the collision process of the non-Maxwellian ionospheric plasma in E region.

Parallel Numerical Model for the Simulation of Gravity Wave’s Nonlinear Propagation

Liu Xiao, Xu Jiyao, Li Wenqiang, Gao Hong

2009, 29(3): 296-303. doi: 10.11728/cjss2009.03.296

Abstract(3393) PDF 896KB(1209)

Abstract:
Based on the idea of MPI (Message Passing Interface) and the domain decomposition, a paralleled numerical model is developed for the simulation of gravity wave's nonlinear propagation. The model is based on the staggered grid system. The domain decomposition technique and data communication between each sub-domain in the staggered grid system are also presented in detail in the paper. The numerical simulation results for the propagation of gravity wave with small amplitude indicate that, the parallel numerical model can reproduce the propagation of small amplitude gravity wave and preserve the energy conservation relation. The parallel efficiency is about 0.65 and can be approximate to its maximum of 1.0 under the perfect conditions. As the comparison with the sequence model, the nonlinear propagation of gravity wave with finite amplitude was simulated by using the sequence and parallel model with different resolutions and the same computational time. The results indicate that, the parallel model can resolve the Kelvin-Helmholtz billows which appear after the time when gravity wave overturns and before the time when the turbulence is excited due to its relative higher resolutions and more processes. But, the sequence model can't resolve the fine phenomena due to its lower resolutions in the same computational time.

Impact of the Uncertainties of Input Parameters on the Atomic Oxygen Density Derived From OH Nightglow

Gao Hong, Xu Jiyao, Chen Guangming, Yuan Wei, Schulte W, Mikhalev A V, Medvedeva I V

2009, 29(3): 304-310. doi: 10.11728/cjss2009.03.304

Abstract(3559) PDF 604KB(1309)

Abstract:
When the atomic oxygen density in the mesosphere and lower thermosphere region is derived by means of photochemical model calculations from OH nightglow emissions, a retrieval uncertainty, i.e. uncertainty of the density values obtained this way arises from the uncertainties of the input parameters. The retrieval uncertainty due to the uncertainties of atmospheric parameters and OH(8-3) band volume emission rate, the retrieval uncertainty due to the uncertainties of rate coefficients, and the retrieval uncertainty due to the uncertainties of all input parameters are analyzed using as an example the sudden death quenching model for OH airglow. The parameters the uncertainties of which have the largest contributions to retrieval uncertainty are found. The results show that all three retrieval uncertainties increase with altitude. The retrieval uncertainties caused by the uncertainties of the temperature and emission rate yield the largest contributions to the first retrieval uncertainty. The retrieval uncertainties caused by the uncertainties of the coefficients b(8) and A(8-3) yield the largest contributions to the second retrieval uncertainty.

Variation Characteristics of Tropopause Temperature and Height
From COSMIC

Yuan Wei, Xu Jiyao, Ma Ruiping

2009, 29(3): 311-318. doi: 10.11728/cjss2009.03.311

Abstract(3698) PDF 736KB(1207)

Abstract:
The global variation characteristics of tropopause are shown by analyzing the data of temperature profiles from Radio Occultation (RO) observations aboard the satellites of COSMIC. These satellites have excellent explorations with global coverage and vertical resolution. The accurate and high vertical resolution temperature profiles from RO/COSMIC provide a unique opportunity to study the global structure and variability of tropopause. The daily mean temperature data from the day 111 of 2006 to the day 295 of 2007 are chosen for the analysis in this paper. The global distributions of tropopause height and temperature and their temporal variation depending on latitude, by using the method of Lapse Rate Tropopause (LRT), are discussed. These results indicate that the global distributions of tropopause temperature and height are consistent with the investigation by some radiosondes and the reanalyses data of the European Centre for Medium-Range Weather Forecasts (ECMWF). There are three important characteristics in the present study: (1) the obvious seasonal variation of tropopause height and temperature, (2) the reversed phase variability of tropopause height between the equatorial, lower latitude and the higher latitude, and (3) the North-South asymmetry of the annual variation of tropopause temperature and height.

Companion Microsatellite in SZ-7 Flight Mission

Chen Hongyu, Zhu Zhencai, Zhou Yilin, Cao Caixia, Yu Yong, Li Dong

2009, 29(3): 319-325. doi: 10.11728/cjss2009.03.319

Abstract(3218) PDF 943KB(1539)

Abstract:
The BX-1 micro-satellite, successfully released from the Shenzhou-7 (SZ-7) module, accomplished the purposes of providing the images of the SZ-7 and demonstrating the ability to inspect the orbital module and conduct proximity operations around the SZ-7 module. The BX-1 was a demonstrator for many new space technologies, including GaInP2/GaAs/Ge solar cells, lithiumion battery, micro-ammonia thruster, micro-attitude tracking controller, camera with double-focusing systems and micro-USB-responsor. The criterion of forming the stable elliptic orbit around the SZ-7 module is discussed in this paper. The evaluation of the BX-1 micro-satellite mission is provided by flight datum.

Study on Space Object Tracking in Space-based Optical Surveillance

Li Jun, An Wei, Zhou Yiyu

2009, 29(3): 326-331. doi: 10.11728/cjss2009.03.326

Abstract(2548) PDF 708KB(1331)

Abstract:
Utilizing space-based observer to achieve effective surveillance on space objects is the direction and trend of the space surveillance. Based on the analysis on the characteristics of the space optical surveillance, the passive tracking method for the surveillance data is put forward, according to extracting the linear moving information of the streak of the space object in surveillance image frame. And the corresponding tracking initiation method is also given. The data flux in information processing is reduced, and the comparative tracking precession can be provided at the same time.

Time Synchronization Method for High Dynamic GPS/SINS Integrated Navigation System

Li Jianwen, Hao Shunyi

2009, 29(3): 332-337. doi: 10.11728/cjss2009.03.332

Abstract(3121) PDF 619KB(1023)

Abstract:
Time synchronization error sources of the GPS/SINS integrated navigation system in high dynamic environment were magnified to different degrees. As a result, the integration capability of the system was badly affected consequently. A thought of designing the synchronized time benchmark and recording the communication delay of the GPS in the hardware was presented. Based on it, the time mark difference between the two subsytem, the drift of the SINS' frequency mark and the communication delay were considered as the synchronization error sources of the system. In order to synchronize the measurements at every synchronization point, the modeling of the drift, the extrapolated calculation of the measurements and the filtering compensation for the communication delay were accomplished using the software processing methods. Simulation results show the efficiency of the method.

Fuzzy Adaptive Compensator Control for Free-floating Space Manipulator With Unknown Payload Parameters to Track Desired Trajectory in Joint Space

Liang Jie, Chen Li

2009, 29(3): 338-345. doi: 10.11728/cjss2009.03.338

Abstract(4350) PDF 761KB(1882)

Abstract:
In this paper, when the case of the attitude of base controlled and its location uncontrolled, we discuss the control for free-floating space manipulator to track desired trajectory in joint space. Combined the relationship of the linear conversation of the system and the Lagrange approach, the full-controlled dynamic equation of free-floating space manipulator are established. Base on above results proposed, aiming at the case of free-floating space manipulator system with uncertain payload parameters, a composite scheme of a computed torque controller plus a fuzzy compensator is proposed to track desired trajectories in joint space. Namely, it will transfer the impact of system's unknown parameters to computed torque controller through fuzzy adaptive compensation system controller, to
ensure the whole closed-loop control system's asymptotic stability with the existence of unknown parameters. The mentioned control scheme can effectively control two joint of space manipulator to stably track the desired trajectory in joint space. It has obvious advantages that with needless feedback and measured the position, velocity, acceleration, attitude angle velocity and attitude angle acceleration of the floating base. At the same time, no requirements for the dynamic equations of the system are linearly dependent on inertial parameters. A two space-based manipulator system is simulated to verify the proposed control scheme.

Status and Demand Analysis of Space-based Observation of Space Environment

Gong Jiancun, Liu Siqing, Shi Liqin, Chen Zhaofeng

2009, 29(3): 346-352. doi: 10.11728/cjss2009.03.346

Abstract(3520) PDF 621KB(1467)

Abstract:
Space-based observation of space environment is not only an important method to understand space environment and its evolution law, but also an important way to obtain principle data source used for the operational space environment prediction to ensure the safety of human space activities. In order to promote the development of space-based observation in China, the characteristics of the current situation of domestic and foreign space-based space environment observation, as well as the operational observing abilities serving the space weather forecast are summarized at first in the paper. Then the space-based observation demand coming from space environment safety insurance operation is analyzed, and a preliminary strategy of domestic space-based observation development of space environment is studied.