2004 Vol. 24, No. 6

Display Method:
ALFVÉN WAVE AND FAST WAVE COUPLING RESONANCE IN CORONAL LOOPS
YE Zhanyin, WEI Fengsi, WANG Chi, FENG Xueshang, LUO Qingyu
2004, 24(6): 401-411. doi: 10.11728/cjss2004.06.20040601
Abstract(2303) PDF 917KB(931)
Abstract:
Complete Orthogonal Function Series Expansion (OFSE) method is generalized and applied to make research about the time evolution coupling process of fast and Alfvén waves in coronal loops. With the OFSE method, intrinsic angular frequencies of coronal loop quasi-modes could be described mathematically and the intrinsic angular frequency of torsional Alfvén waves in every magnetic field line of coronal loops is investigated theoretically and numerically. With the method, the relationship between a coupling driven term and torsional Alfvén wave resonance is analyzed. Numerical result presents wave amplitude features at the coupling resonant place. It is found that: when the footpoint driven angular frequency is not equal to one of quasi-mode intrinsic angular frequencies, at the resonant position with a δ profile of Alfvén wave amplitude, absolute value of radial gradient of fast wave amplitude is very large and approximates a discontinuity, which is necessary to dissipate fast waves. On the other hand, if the footpoint driven angular frequency is equal to one of quasi-mode intrinsic angular frequencies, widespread small scale structure of Alfvén wave amplitude and an approximate discontinuity at resonant plece, which are necessary to dissipate Alfvén waves, appear.
THE STUDY ON BREMSSTRAHLUNG OF PLASMA IN 1 AU DURING QUIET SUN AND SOLAR FLARE PERIOD
SUN Weiying, WU Ji
2004, 24(6): 412-420. doi: 10.11728/cjss2004.06.20040602
Abstract(2702) PDF 685KB(986)
Abstract:
Bremsstrahlung is the main mechanism of energy loss of space plasma when the magnetic field in plasma is weak. The results calculated at 1 AU of Bremsstrahlung radiation show that the variation of emission intensity If has direct relation to the frequency of electromagnetic wave which has been radiated from the plasma. The emission intensity will increase sharply when the emission frequency is close to plasma frequency. The emission intensity will logarithmically decrease slowly when the emission frequency increase. The brightness temperature Tb is proportional to the electron temperature Te and optical depth of the medium. The variation tendency of Tb is consistent with that of If. The emission intensity and brightness temperature in quiet sun period are lower than that of in solar flare at the same emission frequency.
THE INTERPLANETARY MASS EJECTIONS OBSERVED BY HELIOS
DU Dan, LI Changxing, WANG Chi
2004, 24(6): 421-433. doi: 10.11728/cjss2004.06.20040603
Abstract(2472) PDF 975KB(836)
Abstract:
Using abnormally low proton temperature as the primary identification signature of interplanetary mass ejections (ICME), about 160 probable ICME observed by Helios l and 2 between 0.3 AU and l AU have been identified. The resulting list of events enables us to study the radial evolution of ICME in a statistical sense. The occurrence rate of ICME approximately follows the solar activity cycle. ICME expand during propagation in the solar wind; the radial width increase with distance as R0.64. The radial expansion speed of the ICME is of the order of the Alfven speed. The average temperature and magnetic field magnitude inside ICME decrease faster with distance than the ambient solar wind, as expected for an ex panding structure. The relatively slower decrease of temperature with distance than the adiabatic expansion solar wind implies a substantial heating of the ejecta. The average bulk speed of ICME remains constant with distance between 0.3 and 1 AU.
THE NONSTEADY AND NONLINEAR INTERACTION BETWEEN PLASMA WITH THE FIELD IN WAKE REGION OF A MOVING BODY IN SPACE
MA Shanjun, WAN Guoxiang, XU Xuexiang
2004, 24(6): 434-440. doi: 10.11728/cjss2004.06.20040604
Abstract(2187) PDF 770KB(1171)
Abstract:
The interaction between a body in space and its plasma environment is one of the basic problems in space plasma physics. Based on a set of the coupled equations that describe the non-steady and non-linear interactions between plasma and the electromagnetic field in the wake region of a moving body in space, using the method of numerical simulation, the evolutions of the density distributions of charged particles and collapses of electric field are obtained. Considering the property of axial symmetry of field quantity, the initial conditions of two dimensions with three field components and the method of limited differencial, FTCS (time forward-differencial and space central-differencial method), have been used. The initial condition must satisfy the condition of transverse wave ▽·Êȓ,τ=0)=0 and the basic parameters in numerical calculation are V0 = 106cm/s, Te = 2780 K, ne0 = 1 × 105 cm-3, R0 = 100 cm, Ê0 = 0.15. It is noticeable that we take into account the effect of time derivative on the density disturbance and field distribution, which is not considered in previous researches. The results of numerical calculations show that the density cavitons and potential solitons are formed due to the modulational instability. Comparing with the previous works[5]-[7], the velocity of the collapse is faster relatively. By detecting the distribution of density catiton, the moving body can be traced out by means of the change of the density caviton, although the body may be a stealth vehicle which can not be detected by the radar.
GENERAL DISPERSION RELATION FOR THE THREE-WAVE PROCESS OF PARAMETRIC EXCITATION (I) The Preferred Excitation of an Electron Langmuir Wave and an Ion Acoustic Wave
ZHAO Zhengyu, WEI Hanying
2004, 24(6): 441-447. doi: 10.11728/cjss2004.06.20040605
Abstract(2283) PDF 590KB(1052)
Abstract:
Three-wave coupling process in parametric excitation is well studied under an isotropic, homogenous and collisionless ionospheric background. First discussed is the nonlinear coupling between ionospheric eigen oscillations with the presence of incident electromagnetic wave. Then, the dispersion relation of parametric excitation process in collisionless ionosphere is deduced, and two kinds of frequency conditions and wave-vector conditions are obtained for critical excitation of parametric insta bility. It is proved theoretically that the excitation of an electron Langmuir wave and an ion acoustic wave when parametric instabilities occur is the easiest tendency due to the minimum energy consumption.
NEW RESULTS BY SZ-4 ATMOSPHERIC COMPOSITION MEASUREMENT
QIN Guotai, QIU Shiyan, YE Haihua, HE Aiqing, SUN Lilin, LI Hong, ZHU Yiqiang, LIN Xianwen, XU Xuepei
2004, 24(6): 448-454. doi: 10.11728/cjss2004.06.20040606
Abstract(2556) PDF 611KB(1056)
Abstract:
An atmospheric composition detector with a quadruple mass spectrometer on board spacecraft SZ-4 was launched on 30 December 2002. Based on the analysis of the three month’s (2003-01-2003-03) data, during these months the summer just located at the southern hemisphere of the earth, and occurred some geomagnetic disturbances, the new results of the abnormal change of the thermospheric composition (near 330-362 km) are measured first. The results show that the density of N2 clearly increased, in contrast, the density of O showed a decrease, and occurred only at the higher latitudes of the southern hemisphere, during the peak of geomagnetic disturbances. It was quite different in comparison with the results of SZ-2 and SZ-3, where these abnormal change occurred at higher latitude of the northern hemisphere. The reason causing above mentioned phenomena might be related to the en ergetic particle input into the pole and high latitude region which heats the upper atmosphere in a large scale and produce a large scale air upstream which brings the air from lower altitude up to higher altitude and results in the above mentioned abnormal change. These abnormal change occurred at the different hemisphere, it seems that the abnormal change may occur only at hemisphere of Summer season.
GROWTH PROCESS AND PROPERTY ANALYSES OF GaMnSb GROWING ON BOARD OF SZ-3 SPACECRAFT
ZHANG Fuqiang, CHEN Nuofu, WU Jinliang, ZHONG Xingru, LIN Lanying
2004, 24(6): 455-461. doi: 10.11728/cjss2004.06.20040607
Abstract(2297) PDF 810KB(1049)
Abstract:
The GaMnSb sample was grown in Shenzhou-3 spacecraft (SZ-3) under microgravity conditions. The designed ampoule with the alumina felt used as the buffer between the ampoule and the ampoule crucible to overcome the enormous vibration, and was successfully recovered after the space growth of GaMnSb. It indicates that the design is practicable. X-ray energy spectra and X-ray diffraction were applied to analyse the structure property for the space-grown GaMnSb. The results reveal that the GaMnSb sample is polycrystalline. The main reasons are the temperature fluctuation and the energy shortage of the space crystal furnace. The energy shortage resulted in that the seed crystal was not melted, and that the GaMnSb was grown without seed crystal.
SPACE DEBRIS COLLISION PREDICTION RESEARCH
LIU Jing, WANG Ronglan, ZHANG Hongbo, XIAO Zuo
2004, 24(6): 462-469. doi: 10.11728/cjss2004.06.20040608
Abstract(2608) PDF 713KB(1217)
Abstract:
The population of orbital debris is increasing and these debris has serious hazards to spacecrafts in the earth orbit so to form an impact to human’s space activities. In recent decades, researches on space debris and its applications have attracted more and more attentions as a branch of space environmental study. In this paper, the issue of Space Debris Collision Prediction key techniques were studied, there after, the prediction method was established and tested. With large numbers of debris orbital data collected, this method and codes were verified by two collision and avoidance examples so to prove their validity. The conclusion was deduced that developing the collision avoidance technique and applying it into practice is feasible.
THE NEW INVERTED ELECTRIC FIELD MILL
LUO Fushan, HE Yuhui, ZHANG Jian, GUO Hu, CHEN Daren
2004, 24(6): 470-474. doi: 10.11728/cjss2004.06.20040609
Abstract(2161) PDF 441KB(1244)
Abstract:
The paper introduces a new inverted electric field mill. The electric field mill measures the intensity and polarty of atmospheric electric field to forecast the potential thunderstorm and electric shock in local area. It can be used safely as a monitor of the warning in places where are likely regions for the occurrence of static electricity and thunderstorm, for example, meteorological conditions for space-flight, aviation, oil, electric power, mine and open-air stadium.