空间科学学报

2004 Vol. 24, No. 4

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TRANSMISSION AND ABSORPTION OF MICROWAVES BY AN INHOMOGENEOUS SPHERE PLASMA

SONG Falun, CAO Jinxiang, WANG Ge

2004, 24(4): 241-246. doi: 10.11728/cjss2004.04.20040401

Abstract(2271) PDF 457KB(885)

Abstract:
The numerical calculation of the transmission and absorption of microwaves at an arbitrarily incident angle to the inhomogeneous spherically symmetric plasma is presented.The nonuniform sphere is modeled by a series of concentric spherical shells, and the electron density is constant in each shell. The overall density profile follows any given distribution function. By using the geometrical optics approximation and considering the propagation coefficient is complex, as well as the attenuation and phase coefficients are vectors, the detailed evaluation shows that the transmission and absorption of microwaves in the inhomogeneous spherically symmetric plasma depend on the electron and neutral particle collision frequency, central density, incident angle of the microwaves and density distribution profiles.

RADIAL EVOLUTION OF THE PROTON BEAM DENSITY IN THE SOLAR WIND

QAN Zhengrui, TU Chuanyi, Eckart Marsch

2004, 24(4): 247-252. doi: 10.11728/cjss2004.04.20040402

Abstract(2443) PDF 448KB(851)

Abstract:
In the solar wind the proton velocity distributions usually have two maxima. The part of the distribution around the major maximum of the distribution is called the core part, and that around the second maximum is called the beam part. How the proton beam is formed in the solar wind is still a problem to be solved. The radial evolution of the beam density places an observational constraint on the theory. To clarify the issue the plasma data obtained by Helios 2 in high-speed wind with 700 km/s > v_s > 600 km/s was analyzed. And the 3-D proton velocity distributions were integrated to get a 1-D distribution along the magnetic field direction. The mean values and standard deviations of the ratios of the beam density relative to the total proton density in 0.05 AU interval were calculated. It was found that the relative beam density in high-speed wind doesn't increase obviously with increasing heliocentric distance, thus it is concluded that the proton beam probably is formed inside 0.3 AU, and doesn't change much during the solar wind expanding outward.

THE KINETIC ALFVEN WAVE DRIVEN BY THE DENSITY INHOMOGENEITY AND THE MAGNETIC FIELD INHOMOGENEITY IN FINITE β PLASMA

DUAN Suping, LI Zhongyuan

2004, 24(4): 253-260. doi: 10.11728/cjss2004.04.20040403

Abstract(3089) PDF 686KB(937)

Abstract:
Basing on the analysis on the drift wave instability caused by the density and magnetic field inhomogeneities in finite plasmas, we find that this instability has an effect on driving kinetic Alfven waves. The kinetic theory deals with the effect of finite Lamor radius and wave-particle interacting effectively and correctly. According to the motion of charged particles in the electromagnetic field, the Vlasov equation to describe the ion motion and the drift kinetic equation for electron motion were adopted. Comparing the effects on the drift instabilities between the density in homogeneity and the magnetic field inhomogeneity, it is found that the drift instability easily takes pace under the condition of the density inhomogeneity and the energy transfer much faster in this process. Driven kinetic Alfven waves occur after getting the energy from the instability. The numerical solutions indicate that the kinetic Alfven waves can be driven in magnetosphere widely, especially in the obviously inhomogeneous regions such as the cusp, magnetopause and the plasma sheet boundary layer. The results in this paper imply that the kinetic Alfven waves have great influence on the energy transfer in the magnetosphere.

PRELIMINARY ANALYSIS ON LIDAR OBSERVATIONS OF STRATOSPHERIC AEROSOL OVER WUHAN

YU Changming, YI Fan

2004, 24(4): 261-268. doi: 10.11728/cjss2004.04.20040404

Abstract(3296) PDF 708KB(1055)

Abstract:
By using the observations obtained by Wuhan University Lidar system at 589 nm wavelength, vertical profile of aerosol extinction coefficient and temporal behavior of the integrated aerosol backscattering coefficient in the low stratosphere are preliminarily analyzed from March 2001 to January 2002. The analysis results show that there is an aerosol layer between 16 km to 20 km in the lower stratosphere over Wuhan (30.5°N, 114.4°E), and aerosol layer width and maximum scattering ratio shows a seasonal variations. Temporal behavior of the integrated backscattering coefficient of stratospheric aerosol shows a seasonal variations trend, also. The variation range is between 2.2 × 10^-5sr^-1 to 7.0 × 10^-4sr^-1. They reach their maximum value in summer and minimum value in winter, respectively.

CHANGES OF THE ATMOSPHERIC DENSITY AT SZ-3 ORBIT ALTITUDE

QIN Guotai, QIU Shiyan, HE Aiqing, ZHU Yiqiang, SUN Lilin, LIN Xianwen, LI Hong, XU Xuepei, YE Haihua

2004, 24(4): 269-274. doi: 10.11728/cjss2004.04.20040405

Abstract(3002) PDF 540KB(1198)

Abstract:
Atmospheric density detector was on board spacecraft SZ-3 launched on March 2002. At SZ-3 orbit altitude (330--410 km) atmospheric density data were collected near half year. The results show that in the rather quiet period of solar and geomagnetic activity, the difference of the atmospheric density between the sunshine and shade area is one of the principal change of thermosphere density, the highest ratio of atmospheric density in the sunshine to the density in the shade reaches about 3.0, and correlate with solar and geomagnetic activity; During 2002-04-17 and 2002-04-19 two strong geomagnetic disturbance events, the globe thermosphere density obviously increases and amplitude of the increase reached about 60%, and shows a positive correlation with a delay of about 6—7 h; The abnormal disturbance of atmospheric density were observed in the 30°N—40°N during these strong geomagnetic disturbance events; The thermospheric density changes with the value of F_10.7 which represents the solar activity level and exhibits a obvious correlation.

SPECTRAL CHARACTERISTICS OF DAILY RANGES OF Z COMPONENT AT GUANGZHOU GEOMAGNETIC STATION

MA Ruiping, XU Jiyao

2004, 24(4): 275-282. doi: 10.11728/cjss2004.04.20040406

Abstract(2482) PDF 775KB(942)

Abstract:
Using the geomagnetic data of daily variation of Z component observed from 1972 to 1993 at Guangzhou station, the low frequency components that include the annual average, the annual variation and the semiannual variation, and the short period component with periods less than 60-day are analyzed year after year. The daily averages of the F_10.7 also are analyzed. The daily variations of Z at Guangzhou station can approximately reflect the magnitude of the equatorial electro jet. The results show that, the annual averages of daily variations of Z are favorably linearly correlative with the annual averages of the F_10.7; the annual variation with the amplitude of about 5 nT and summer maxima is existent in every year, it is not virsually correlative with the solar activity and it is a seasonal effect; the semiannual variation with equinoctial maxima is existent, the amplitude of the semiannual variation is obviously greater at solar maximum than at solar minimum, for example, the amplitude of the semiannual variation is about 10 nT at 1981 that is the year of solar activity maximum, but the amplitude is about 2 nT at 1976 that is the year of solar activity minimum; the oscillation with period about 27 day which relate to solar rotation and the oscillations with periods close to 16, 10, 5, 2 d which relate to the planetary wave are obviously existent. The spectral characteristics of the geomagnetic daily ranges of Z at Guangzhou station prompts further investigation into the physical mechanism of that the ionosphere is affected by the middle and lower atmosphere.

FORECAST OF THE ENHANCEMENT OF RELATIVISTIC ELECTRON AT THE GEO-SYNCHRONOUS ORBIT

XUE Bingsen, YE Zonghai

2004, 24(4): 283-288. doi: 10.11728/cjss2004.04.20040407

Abstract(2361) PDF 538KB(1137)

Abstract:
The high flux of energetic electrons on geo-synchronous orbit can induce many kinds of malfunction of the satellite there, within which the bulk charging is the most significant that several broadcast satellite failures were confirmed to be due to this effect. The electron flux on geo-synchronous orbit varies in a large range even up to three orders accompanied the passage of interplanetary magnetic cloud and the following geomagnetic disturbances. Upon the investigation of electron flux, interplanetary solar wind data, and geomagnetic data as well, we found that, (1) The enhancement of energetic flux on the geo-synchronous orbit exhibits periodic recurrence of 27 days; (2) significant increase of electron flux relates to interplanetary index and characters of their distribution; (3) the electron flux also has relation to solar activity index. In our research work, artificial neural net was employed and constructed according to the job. The artificial neural network was employed in this paper to build the relationship between the electron flux and interplanetary parameters. The input parameter is: the solar wind velocity in km/s; the density of the plasma density; the total strength of interplanetary magnetic field. All of them were daily average value. To represent the influence of the variation of the interplanetary parameters influence, the ratio with those of the previous day of the mentioned parameters were also input. Through the training, the neural network can adjust the internal weight and the value of the nods to build the relationship between the electron flux and the interplanetary parameters and their variation. Preliminary result showed that the accuracy forecast of electron flux 1 day ahead can reach 80%. Through the effort in the prediction of energetic electron fluxes enhancement with the solar wind and interplanetary magnetic field parameters, we realized that the mechanism of the electron event is far too complex to be described with simple formulas. Large database is needed for statistic work to make the prediction more accurate. Fundamentally, great measured and advance research work has to be done to investigate the source energetic electron and acceleration mechanism.

A STUDY ON SPACECRAFT INTERNAL CHARGING WITH MONTE CARLO METHOD

GAO Bingrong, HAO Yongqiang, JIAO Weixin

2004, 24(4): 289-294. doi: 10.11728/cjss2004.04.20040408

Abstract(2234) PDF 561KB(1203)

Abstract:
Dielectric internal charging caused by energetic electrons will cause anomalies in Geosynchronous satellites, so it is an important problem faced by satellite designer. In recent years, many statistical studies have been conducted in this area. In this paper, Monte Carlo method has been used to simulate the charge deposition in the dielectric caused by energetic electrons. The electric field in the dielectric was calculated as the function of injected electron energy, thickness of shielding and dielectric. It is found that the electric field induced by the deposited charges in the dielectric has significant correlation with these three factors.

INTEGRATED FLOW HEAT AND MASS TRANSFER ANALYSIS IN LARGE SPACECRAFT

XU Xiaoping, ZHONG Qi, FAN Hanlin, LI Jingdong

2004, 24(4): 295-301. doi: 10.11728/cjss2004.04.20040409

Abstract(2341) PDF 716KB(1002)

Abstract:
The air flow field in a large spacecraft was analyzed by the method of numerical simulation under conditions of low velocity, room temperature and laminar flow's assumption. Effects of the condenser, air cleaner, fans and other objects in the spacecraft on the air flow field were observed, and corresponding influences of flow field to distributions of temperature, humidity and carbon dioxide concentration inside the spacecraft were presented. Accordingly, the transport of mass and energy by airflow was evaluated and a theory of whole-flow-field-design in the large spacecraft was brought forward. In this theory, a novel design to construct the whole flow field with circumfluent and the partial flow field cooperating with diffusion of mass and heat was emphasized, from the whole system point of view. That was, equipments in spacecraft must be arranged in specified place to result in circumfluence in the whole flow field, and the partial flow field was designed to cooperate with diffusion of heat, water and carbon dioxide source. Comparisons of some parameters e.g. average velocity and velocity un-uniformity coefficient of flow, were carried out between the recoverable module and the orbital module of the spacecraft, and the results well approved the novel theory above.

THE DEVELOPMENT AND STATUS OF SPACE X-RAY IMAGING TELESCOPE

LI Baoquan, ZHU Guangwu, LIN Huaan, WANG Shijin, PENG Jilong

2004, 24(4): 302-311. doi: 10.11728/cjss2004.04.20040410

Abstract(3244) PDF 1105KB(1119)

Abstract:
With the development of space technique, the space systems are becoming more and more complicated, but they are more and more susceptible to space weather. Consequently, space weather forecast is being widely researched in the world. The great impacts on the normal life of human made by space weather are presented in this paper. The importance about solar X-ray imaging in space weather forecast is expatiated on. The fundamental principle, the principal design and the instrument characteristics of celestial and solar X-ray grazing imager operating successfully in space are introduced. The principal technical indices of solar X-ray imaging telescope (SXIT) which is being developed in China are presented. The SXIT integrates the gracing incident telescope and the normal incident telescope and operates in the 0.4--10 nm X-ray band interval and the 19.5 nm EUV band. It can provide the high resolution solar disk imaging for its 45 arcmin field of view and 5 arcsec spatial resolutions. The SXIT is the newest solar storm monitor at present. The SXIT extends the temperature response to the coronal plasma and enhances the sensitivity to the coronal plasma with lower temperature, so more signatures and precursors of the solar eruption can be observed by the SXIT. The SXIT is dedicated to domestic space weather forecast. It will firstly fly on the FY-4 serial meteorological satellites that operates on a geostationary orbit, so real-time data for space weather forecast can be obtained 24 hours per day. The SXIT will greatly enhance the ability of the domestic space weather forecast and the research of solar physics if it operates successfully on orbit.

DESIGN AND DYNAMIC ANALYSIS OF A DRIVING SYSTEM FOR ROD-CABLE DEPLOYABLE MAST

SU Bin, GUAN Fuling, YANG Dabin, YANG Zhi

2004, 24(4): 312-320. doi: 10.11728/cjss2004.04.20040411

Abstract(2247) PDF 972KB(796)

Abstract:
The technique requirements, basic driving principles and designing methods of a motorized drive system for a kind of rod-cable deployable mast has been introduced in this paper. Three different kinds of driving system scheme are compared and the best one is chosen for the calculated model. Finally, the dynamic analysis of this mechanical system is presented.