空间科学学报

2003 Vol. 23, No. 3

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PROPAGATION AND EVOLUTION OF INTERPLANETARY SLOW SHOCK

HU Youqiu, SUN Shuji

2003, 23(3): 161-167. doi: 10.11728/cjss2003.03.20030301

Abstract(2630) PDF 675KB(1034)

Abstract:
Using a two-dimensional, ideal MHD model, this paper investigates the evolution of a slow shock in the solar wind in the heliospheric equatorial plane （2-D, 2-component model） and the heliospheric meridional plane （2-D, 3-component model） respectively. It is shown that the slow shock evolves into a shock system that consists of the original slow shock and a newly formed fast shock. The shock system is nearly symmetrical with respect to the central normal of the slow shock source in the heliospheric meridional plane, whereas it is asymmetrical in the heliospheric equatorial plane. There exists a touch point between the fronts of fast and slow shocks, at which the two shocks merge and degenerate into a gas-dynamic shock. The touch point deviates eastward with respect to the central normal of the shock source, and the deviation angle increases during the outward propagation of the shock system. A preliminary analysis shows that the east-west asymmetry of the propagation and evolution of the slow shock in the heliospheric equatorial plane is mainly attributed to the spiral structure of the interplanetary magnetic field.

THE DEVELOPMENT OF PROTON BEAM IN THE SOLAR WIND

WANG Linghua, TU Chuanyi, AO Xianzhi

2003, 23(3): 168-173. doi: 10.11728/cjss2003.03.20030302

Abstract(2330) PDF 576KB(1043)

Abstract:
In this paper a new mechanism to form the proton density distribution to explain the radial evolution of the relative beam density （n_b/n_p） is suggested. It is found that it is the resonance between protons and cyclotron waves that drives the protons to form such a unique distribution. First, several possible cyclotron waves are calculated to give the cold plasma dispersion relation. Among those possible waves, the waves propagating outside will play an essential role in the beam distribution formation and the waves propagation both inside and outside will help the core distribution formation. With the axial symmetry assumption, the quasi-linear two-dimensional diffusion equation are solved numerically by using Lax-Wendroff and FTCS scheme combining cold plasma dispersion relation and wave-particle resonant condition. The boundary conditions are not the common ones. A specific explanation about the conditions is given. In the simulating process, an original isotropic proton velocity distribution and the plasma dispersion relations remain constant are assumed. Thus, with diffusion equation we simulated the transformation of solar wind proton density as it flowed from 0.35 AU to 0.9 AU. The contours of proton density distribution show explicitly that the core and beam parts of proton density distribution. In the solar wind plasma, with increasing heliocentric radial distance, the Alfven velocity decreases and more and more protons can be resonant with the second-branch left hand polarized waves, so a part of core protons can enter into beam distributions and become beam protons. From the numerical distribution the radial variation of proton density from 0.35 AU to 0.9 AU and is obtained the calculated results are compared with observed results. Although the cold plasma dispersion relation is assumed, which is not a self-consistent assumption, the simulating results are accordant with the observations. The result shows clearly that the ratio of proton beam number density to proton core number density increases with increasing heliocentric radial distance.

TRANSPORT OF RELATIVISTIC ELECTRONS FROM UPSTREAM SOLAR WIND INTO GEO-SYNCHRONOUS ORBIT

LIU Xiaolong, ZHAO Hua, C.T. Russell, PU Zuyin, LIU Zhenxing

2003, 23(3): 174-180. doi: 10.11728/cjss2003.03.20030303

Abstract(2516) PDF 556KB(766)

Abstract:
A new mechanism is brought forward to explain the tremendous relativistic electron flux enhancement events at the geo-synchronous orbit. There have been two explanations advanced before. The first theory says that the magnetic storms cause the relativistic electron flux enhancement events; according to the second one, it is the disturbance of the higher velocity branch of the solar wind that results in the events. However, in the events starting on July 14, 2000, which were studied, there had no evident disturbance of the velocity of the solar wind and the magnetic storms lagged behind the relativistic electron flux enhancement. In the present paper, we separately simulate the motions of the relativistic electrons in the x-dependent Harris-like equilibrium model and a more realistic magnetic model-T96 Model of Tsyganenko. According to the results of numerical simulation, we suggest that: when the IMF directed southward, the magnetic re-connection occurred at the dayside magnetopause. Therefore, the relativistic electrons can move to the magnetotail from the dayside magnetopause, then the electrons reached the geosynchronous orbit from the tail region by stochastic motion in the current sheet.

INTERACTION BETWEEN THE POWERFUL HIGH-FREQUENCY RADIO WAVE AND THE LOWER TERRESTRIAL IONOSPHERE

HUANG Wengeng, GU Shifen

2003, 23(3): 181-188. doi: 10.11728/cjss2003.03.20030304

Abstract(2121) PDF 672KB(1377)

Abstract:
The terrestrial ionospheric plasma can be heated by a powerful ground-based high-frequency radio wave, which results in the disturbance of the electron temperature and density. In this paper, a self-consistent model of interaction between the powerful HF radio wave and the lower ionosphere is presented. In this model, the self-absorption effect of radio wave is emphasized. For specific transmitter’s parameters （in this paper, P_ER = 200 MW, f= 7.0 MHz are used, which is at the range of many transmitters）, under the daytime ionospheric background, the calculated results show that the self-absorption effect is obvious, when h ＜ 90 km, but the effect can be ignored for h ＞ 90 km. The results also show that the maximum electron temperature enhancement is at the altitude of 70 km, which is three times of the undisturbed background. With the assumption of a recombination in lower ionosphere, the percentage of electron density enhancement is decreasing with the increase of ionospheric heights. For example, at the altitude of 70km, it is 55% or so, but at 120km altitude, it is about 4%.

A NUMERICAL STUDY ON THE GRAVITY-WAVE PACKETS EXCITED BY TWO-VARIABLE WAVE-LIKE DISTURBANCES

HUANG Chunming, ZHANG Shaodong, YI Fan

2003, 23(3): 189-196. doi: 10.11728/cjss2003.03.20030305

Abstract(2280) PDF 669KB(1008)

Abstract:
By using the spectral allocation method, the energy propagation and the characteristics of energy conversion in the excitation of gravity waves by initially given two-variable wave-like disturbances is numerically studied. The simulation results show that when the relative amplitudes and phases of the two initially given wave-like disturbance variables satisfy strictly the polarization relation of gravity waves, only this two-variable disturbance which variables are horizontal wind and temperature can restrict the downward energy propagation of gravity waves. In general cases, A two-variable wave-like disturbance will excite two gravity-wave packets, one propagates upward and the other downward, moreover, the ratio of wave energy for those two gravity waves is decided evidently by the relation of the amplitudes for the two initial disturbance variables, when the ratio satisfies certain condition, only one upward propagating gravity wave can be excited. Further numerical analysis shows that, both the energy propagation paths and velocities in all numerical cases are identical with each other. Compared with the results of energy conversion for gravity waves excited by single-variable disturbances, the characteristic times of the energy conversion for gravity waves in the cases present in this paper are the same, but the efficiencies of energy conversion are larger.

LIDAR OBSERVATIONS OF THE MESOSPHERIC Na LAYER OVER WUHAN: SEASONAL AND NOCTURNAL VARIATIONS

MAO Fei, YI Fan

2003, 23(3): 197-204. doi: 10.11728/cjss2003.03.20030306

Abstract(2623) PDF 752KB(7179)

Abstract:
Based on the lidar observations between March 2001 and October 2002, the characteristics of background Na layer over Wuhan （30.5°N, 114.4°E） are presented and compared with other reported lidar measurements, especially with that of Ur-bana （40°N, 88°W）. The sodium abundance in Wuhan reaches a maximum value in November which is approximately 2.5 times larger than that in April. In November and May, the layer centroid height reaches its minimum and its maximum in April, September and December. The yearly averaged rms width is 4.47km. There is a variation trend in the parameters of Na layer. Especially, the layer rms width shows a semiannual variation trend. The sodium layer abundance generally increases through the night. After rapidly ascending from sunset, the layer centroid height climbs up slowly between 2000 LT and 0500 LT, then descend swiftly. The sodium layer rms width shows about 1.3km variation during the night. At first the layer rms width diminishes, after arriving at a minimum at 0035 LT, it increases steadily with time.

WAVELET ANALYSIS OF YEARLY GEOMAGNETIC SUDDEN COMMENCEMENT SERIES

LE Guiming, YE Zonghai

2003, 23(3): 205-211. doi: 10.11728/cjss2003.03.20030307

Abstract(2422) PDF 693KB(954)

Abstract:
The coronal mass ejections （CMEs） are the most important source causing calamitous space weather. If a CME carries strong southward magnetic field component and last for a prolonged period of time then it can cause geomagnetic storm with sudden commencement, otherwise it just causes geomagnetic sudden commencement. Both geomagnetic activities have sudden commencement. The paper analyzes the geomagnetic sudden commencement number （GSCN） series with wavelet technique to get its periodic properties and the results show that the most evident periods of the GSCN are the periods around 11 years, the strongest period of the GSCN is 10.556 years and reaches its maximum in the year 1948. Two weaker periods of the GSCN are the periods during 16-32 intervals and the periods during 32-64 intervals. The strongest period for the interval 16-32 years is 24.25 years, while the strongest period for the interval 32-64 years is 42.22 years. The paper also computes the correlation coefficient between sunspot number series and geomagnetic sudden commencement number series, the correlation coefficient of the two series is 0.8896. The correlation coefficient of the sunspot number series and geomagnetic storm with sudden commencement number series is 0.8492 which is lower than 0.8896. Though the correlation coefficient of the sunspot number data series and geomagnetic sudden commencement is high, the periodic properties of the two series are not the same. Firstly the periods of the GSCN around 11-year are not the same for the two series, secondly the periods between 16-32 years of the GSCN are more evident than that of sunspot number series, thirdly the periods between 16-32 years of the sudden commencement series are still more evident than that of sunspot number series.

MODELING AND SIMULATION OF INTEGRATED POSITIONING WITH DOUBLE SATELLITE AND GIS

ZHENG Chong, WU Jie, JIANG Qinxue

2003, 23(3): 212-217. doi: 10.11728/cjss2003.03.20030308

Abstract(2248) PDF 499KB(1062)

Abstract:
Local positioning system with only two Geosynchronous satellites can provide not only positioning but also telegram service. In 80 s of 20th century positioning test with two satellites was successfully conducted. In 90 s of 20th century attitude determination using two satellites was also accomplished. A new method of positioning using double satellites and geographic information system （GIS） is presented in this paper. The principle of the method is discussed, and the computer simulation is accomplished. The precision analysis of integrated positioning indicates that the method can improve the positioning precision remarkably. In certain condition, the mean square error can be less than 10 meters.

CONSTELLATION DESIGN BASED ON THE ANALYZING CHARACTER OF CONTINUOUS COVERAGE

HU Jun, CHEN Bo, WANG Jianyu, ZHU Zhencai

2003, 23(3): 218-225. doi: 10.11728/cjss2003.03.20030309

Abstract(2355) PDF 610KB(844)

Abstract:
In this paper, design of constellation in need of continuous coverage for ground target is studied. The equations of two variables, gap time of satellite coverage and gap time of plane coverage, which having essential influence on the coverage capability are inferred. They are calculated in the case of constellations with various deployments. Finally, the inferences are validated using the engineer simulation software STK. This paper provides theoretical guidance for constellation design through theoretical analysis, calculated examples as well as engineering simulation.

METHOD OF SATELLITE FAULT DIAGNOSIS APPLYING EVIDENCE REASONING THEORY TO MERGE INFORMATION

YANG Tianshe, YANG Kaizhong, CAO Yuping

2003, 23(3): 226-232. doi: 10.11728/cjss2003.03.20030310

Abstract(2159) PDF 588KB(965)

Abstract:
It is difficult to diagnose some faults of satellites using the knowledge of only one symptom field. Based on Evidence Reasoning Theory, this paper introduces a new method to diagnose the faults. Information of different symptom field of satellite faults is merged by use the new method, thus the faults can be located more accurately. Firstly, the necessity of applying Evidence Reasoning Theory to merge the information in satellite fault diagnosis is analyzed. Secondly, the theoretical method of applying Evidence Reasoning Theory to merge information of different symptom field of satellite fault is studied. Thirdly, the practical application of the method is given. Fourthly, the notations that should be paid more attention to are analyzed. Finally, the conclusions of this paper are given.

THE ELECTROPHORETIC SEPARATION EXPERIMENTS ON THE WEIGHTLESS AIRCRAFT

JIANG Yuanda, ZHANG Zhiyuan, WANG Haibo, LIU Wenxi, ZHOU Shunlin, FENG Xuezhang, WU Hanji

2003, 23(3): 233-239. doi: 10.11728/cjss2003.03.20030311

Abstract(2386) PDF 655KB(996)

Abstract:
This paper presents the separation experiments and results by a A3-1 continuous free-flow electrophoresis device on board the Russian weightless aircraft. The A3-1 device consists of power conditioning unit, detection unit and electrophoresis unit. The power conditioning unit converts 27V DC coming from the bus into the power sources required for electrophoresis unit. The detection unit has a video tape recorder used for recording the separation picture and a single chip which control the power supply, the detecting, record and storage of operating data. The electrophoresis unit is a electrophoresis separation system in which the rectangular separation chamber has the following internal dimensions: 270 mm long, 60 mm wide, and 3 mm thick （gap）. During operation of A3-1 device, the separation process is monitored with a CCD head placed the front of separation chamber and recorded in the video tape recorder （Video Hi8） in the detection unit. The carrier buffer （the electrode buffer is the same）, used for all experiments, contains 3.5 mMol TEA （Triethanolamine）, 0.7 mMol NaAc and 10% glycerol. The sample to be separated is a kind of mixture containing two colored model proteins, Hemoglobin （HB, yellow） and Cytochrome c （red）. The flight test was performed for tour times. For each flight the aircraft would conduct 10-12 parabolic flights and lasted nearly one hour. The pictures of elec-trophoretic separation and the experimental data were obtained. The results showed that the A3-1 CFFE device worked well and the effect of gravity change on the elec-trophoretic separation process of biological samples can be seen clearly from the pictures. The shape of sample filament is different under different flight state. The filament under the horizontal flight （near 1 g） appears spread and bent to the right near the outlet. The filament under the overweight （1-2 g） flight is not clear due to serious spread, the separation of sample was bad. But the filament under the micro-gravity （0-0.4 g） condition is quite clear （less spread） and almost in a straight line. It was shown that the microgravity environment is beneficial to the electrophoresis separation of biological material.