2002 Vol. 22, No. 3

Display Method:
APPLICATION OF NON-OSCILLATORY, NON-FREE PARAMETER DIFFERENCE SCHEME ON SIMULATION OF SOLAR WIND FLOW IN A HELMET MAGNETIC STRUCTURE
YE Zhanyin, WEI Fengsi, WANG Chi, FENG Xueshang, SHI Yong, YAO Jiusheng
2002, 22(3): 193-202.
Abstract(2108) PDF 317KB(768)
Abstract:
An algorithm called NNDMHD for the two-dimensional, three-component, eight-variable and time-dependent magnetohydrodynamic (MHD) conservative equations is proposed. It reduces Lorentz force error caused by numerical magnetic field divergence's non-zero error in a method of dividing magnetic field into two parts, a potential one invariant of time and a non-potential one varying with time. Then, NNDMHD could be developed from the Non-oscillatory, Non-free parameter Difference scheme (NND), which is very effective in numerical simulation of gas-dynamical transonic flow. At first, numerical tests on NNDMHD are carried out on a typical one-dimensional Riemann case and a two-dimensional Orszag-Tang example. The good numerical results agree with those of references and exhibit no non-physical oscillation near discontinuities. Then, example of solar wind flow in a helmet magnetic field structure being axisymmetric in meridian plane is taken for NNDMHD numerical test. In this example, although physical variables vary in a large scale (-10-4) in radial direction, NNDMHD can still reduce Lorentz force error caused by numerical magnetic field divergence's non-zero error. The numerical result in this example shows that: although the grid mesh is coarser four times than that of usual one, NNDMHD can still keep stable in computation for final steady state result.
THE MAGNETIC STORM RESULTED FROM THE INTERPLANETARY SHOCK OF FEBRUARY 21, 1994
LIU Shaoliang, GUO Jianguang, ZONG Qiugang, B. Wilken, FU Suiyan
2002, 22(3): 203-211.
Abstract(2784) PDF 862KB(835)
Abstract:
On February 21, 1994, at 0903 UT a strong interplanetary shock crossed the Geotail spacecraft while it is at (x, y, z)GSE = (-26.9,60.8, -2.3) Re. The shock hasalso been observed or detected its effect by other satellites such as Imp-8, Goes-6, Goes-7 and Lanl successively. This shock resulted in magnetic index Dst dropped down to lower than -100nT and AE shows an explicit increase. At the same time the geomagnetic field fluctuated intensively, the flux increased of various energetic particles at geosynchronous orbit. These means there are notable energy coupling between the solar wind and the magnetosphere. Gonzalez et al. pointed out the IMF Bz component should be lower than -10 nT and its duration longer than 3 hours for a strong magnetic storm, of which, Dst index lower than -100 nT, but the character of the shock studied in this paper is that there have no long duration of IMF southward Bz event but only large amplitude fluctuation northward and southward in the downstream of the shock, furthermore the enhanced value and average value for the - Bz is lower than that for the +Bz. If we think that the energy transfer from the solar wind into the magnetosphere take place only during IMF Bz component is negative, then this means the rate of energy transferred into ring current is far quicker than the dissipation of the ring current. This result shows that the duration time of southward IMF is not the essential condition for energy transfer from solar wind into the magnetosphere, if the southward IMF has large amplitude and short time-duration, but repeated many times there may be accumulated notable energy in the ring current owing to the rate of ring current dissipation is very slow relative to the rate of energy pouring into the ring current. In addition, for above result we have analyzed the power spectrum property of the magnetic field, it is shown that the disturbance magnetic energy enhanced near five times after the disturbance field crosses the bow shock and the magnetopause. Nakada et al. pointed out that disturbance field in magnetosphere which frequency is in some band would destroy the third adiabatic invariant for some particles but maintain the first and second invariants of them, these particles will spread inward and get energy in this process. The spectrum analysis in this paper shows that the Bz component of the disturbance field in magnetosphere is absorbed notably near 1 × 10-4 Hz, we inferred that this low frequency field may be a reason which resulted in the ring current particles (such as oxygen ion, proton and so on) diffused inward and enhanced their energy, this process have been reported by Fu et al. by means of CRRES/MICS in 2001.
OBSERVATIONAL STUDY OF IONOSPHERIC TEC DURING THE MAGNETIC STORM ON APRIL 6—8, 2000
ZHANG Donghe, XIAO Zuo, GU Shifen, YE Zonghai
2002, 22(3): 212-219.
Abstract(2211) PDF 777KB(830)
Abstract:
One large coronal mass ejection (CME) occurred in the Sun at 1642UT, Apr. 4, 2000. At about 1600 UT, Apr, 6, the high speed solar wind was detected by ACE satellite, the speed of which increased suddenly from 380 km/s up to 600 km/s. Then a southwards interplanetary magnetic field that lasts for 7 hours was observed. The solar wind push magnetosphere, and a large magnetic storm happened near the earth. At 0000 UT, Apr. 7, 2000, the Kp index reaches 8 and lasts for 6 hours. The minimum Dst index is -318 nT. During the magnetic storm, an ionospheric storm was also happened over the region of China shown by the observations of the ionosondes. Combining the temporal ionospheric TEC curves and the curves of the corresponding sub-ionospheric point derived from GPS measurements observed at Beijing, Wulumuqi, and Wuhan GPS stations, the morphology of ionospheric TEC over the region of 30°N-45°N and 85°E-120°E during the magnetic storm occurred on April 6-8, 2000 is studied. The results showed that, a weak negative storm over this region happened between 0200 BT and 0700 BT on April 7, 2000. Compared with the TEC on April 6, the largest value of TEC change is -8TECU. After 0800 BT, a strong ionospheric negative storm appeared over higher latitude region and became stronger and stronger with time. Meanwhile, an ionospheric positive storm developed over lower latitude region between 0700 BT and 0900 BT. During this period, the negative storm over higher latitude became gradually stronger, and moved southwards. Nevertheless the positive storm over lower latitude experienced an enhancing and declining process.
THE CONVECTION ELECTRIC FIELD MODEL IN THE MAGNETOSPHERE
ZHANG Tianhui, XU Ronglan, LI Lei
2002, 22(3): 220-226.
Abstract(1905) PDF 703KB(1037)
Abstract:
Taking the magnetic field lines as the equipotential lines, the convection field in the polar region at the ionospheric heights can be mapped into the magnetosphere where the electric field play a key role in various physical phenomena. To do this, a convection electric field in polar region and a magnetic model of magnetosphere are needed. In this paper, Volland's convection electric field model in the polar region and Tsyganenko's magnetic field model (T89) are used. It's not surprising that the electric field mapped from polar region is not a uniform dawn-dusk field. The results indicate that only in the distant magnetotail, the convection electric field can be considered as uniform dawn-dusk electric field. While, in the other region, there is not only the dawn-dusk electric field (Ey) but also the Ex and Ez. There exist three different regions in the magnetotail whose convection electric field has different characters. These characters are discussed. Generally, the dawn-dusk electric field become stronger and stronger when going from the distant magnetotail to the region near the earth. On the other hand, the electric field is stronger near the dawn and dusk magnetopause boundary than in the mid-plane.
THUNDERSTORM QUASI-ELECTROSTATIC (QE) FIELD AND THE IONIZATION OF NIGHTTIME LOWER IONOSPHERE
HUANG Wengeng, GU Shifen
2002, 22(3): 227-233.
Abstract(1919) PDF 660KB(1050)
Abstract:
Lightning plays an important role not only in the global circuit, but also in the coupling of troposphere-mesosphere-lower ionosphere. It is responsible for some optical phenomena occurring in the upper atmosphere, such as 'sprites', which occur above thunderstorms at altitudes typically ranging from 50 to 90 km. In this paper, a simple point charge model is used to calculate the dependence of amplitude of quasi-electrostatic field on altitude after the thunderstorm discharge completed. By comparison with the disk charge model, we find the point charge model is in good agreement with the former. Since the upper ionospheric boundary are ignored in both models, the calculated thunderstorm QE field is an approximate results. Using the ratio of the electric field to the total atmospheric neutral density as the input parameter, with some reasonable assumption, the Boltzmann equation is solved numerically to decide the disturbance in nighttime lower ionosphere. The results show that the QE field could be greater than the breakdown electric field of the neutral atmosphere between about 70-90km, within about 10ms, which can produce the avalanche ionization of neutrals. As a result, the electron density increases dramatically in these regions. Because the effective time of QE field in ionosphere is very short, the enhancement of electron density will be transient, and the nighttime lower ionospheric disturbance will be recovered to the normal level in a short time. The recovery time depends on the ionospheric altitude due to the different conductivity at different heights in the lower ionosphere.
ACQUIREMENT AND ANALYSIS OF HIGH ACCURATE DOPPLIONOGRAM
YUAN Zhigang, NING Baiqi, WAN Weixing
2002, 22(3): 234-239.
Abstract(2181) PDF 610KB(1070)
Abstract:
The Doppler shift of radio wave echoes reflected from ionosphere is an important parameter to observe ionospheric movements. Generally, high resolution Doppler shift could be obtained in drift mode with digital ionosonde. In this mode, only a few working frequencies are used, so ionospheric disturbance profile with height cannot be acquired. However, in ionogram mode, though Digisonde works with many sounding frequencies, the resolution of Doppler shift is too low to detect ionospheric disturbances precisely. In this paper, a new analysis method is given based on the fact of narrow band of ionospheric echoes, through converting sixteen Doppler channel data to temporal domain by IDFT and estimating the phase differences of adjacent time by least square method, the high accurate doppliono-gram could be acquired in ionogram mode. In order to prove the effectiveness of the method, some experiments have been carried out with Digisonde-256 at Wuhan Ionospheric Observatory. The experimental results have revealed that the high accurate Dopplionogram can be acquired, and the present method is very useful in experimental investigation of ionospheric disturbances.
A NUMERICAL RESEARCH OF NONLINEAR PROPAGATION OF GRAVITY WAVE PACKETS IN THREE-DIMENSION NONISOTHERMAL ATMOSPHERE AND HORIZONTAL WINDS
WU Shaoping, YI Fan
2002, 22(3): 240-248.
Abstract:
A numerical simulation of nonlinear propagation of gravity wave packets with Gaussian distribution in a three-dimension nonisothermal atmosphere, homogeneous and sheared horizontal winds is presented in this paper. By using FICE scheme, the model solves the fully nonlinear, time dependent, three-dimensional fluid equations. The whole propagation process of the gravity wave packets are showed, the propagation characteristics of nonlinear propagation and the influence of background winds, temperature on gravity wave's propagation are analysed. Although there exits the nonlinearity, the basic characteristics of nonlinear propagation are in agreement with that of the linear propagation. During the propagation process, the phases of waves move downward, the wave packet and the wave-associated energy propagate upward and wave disturbed velocity increases with the height. The calculation results also show that wave disturbed velocity increases less than the results expected by WKB approximation. There is difference between the simulation calculations and the results given by WKB approximation on energy trace and group velocity. This indicates that the nonlinearity affects the characteristics of gravity waves. The inhomogeneous temperature lowers group velocity and changes the path of energy propagation. The sheared horizontal winds decreases range of horizontal disturbed velocity's amplitude and the vertical wavelength of gravity wave packet, the vertical wavelength reduces from 10km at altitude of 60km to 4km at altitude 83km. When propagating in the sheared winds, the mean vertical energy flux of gravity wave packet reduces with the height, this implies there is energy exchange between the background winds and gravity wave packet which leads to the coupling of different layers of atmosphere.
A METHOD ON THE PRECISE ORBIT DETERMINATION FOR LUNAR SATELLITE
LIU Yingchun, LIU Lin
2002, 22(3): 249-255.
Abstract(2060) PDF 549KB(1067)
Abstract:
Lunar satellite is the most popular concept in the recent and future lunar exploration missions, such as Clementine (NASA, 1994), Lunar Prospector (NASA, 1998) and Smart-1 (ESA, 2002). The scientific goals of these missions, such as the global mapping, the determination for the high resolution of the lunar gravitational potential and the lunar mass, require the precise orbit determination support. Comparing with that of the Earth satellite, the motion of the lunar satellite could still be regarded as a perturbed two-body problem. However, it is complicated by the fact that the Moon, as the central body of the satellite, is different from the Earth, such as it is rotating slowly, it has no atmosphere, and its harmonic coefficient of the oblate, J2, isn't much larger than other harmonic coefficients. All of these bring us both the advantage and the disadvantage in building an analytical perturbing theory for the lunar satellite. And the corresponding analytical solution of the motion is not the same as that of the Earth satellite. It is not convenient to use the analytical theory directly during the procedure of orbit determination. A numerical method that combines with some properties of the analytical method seems to be a wise choice, which is investigated in this paper. Since the lunar satellite is usually in the polar orbit for finding the water, we use a set of non singular orbital elements to discuss the precise orbit determination for lunar satellite, which is suitable for the lunar orbiter with 0≤e <1 and 0°≤ i < 180°. Then we could take the most advantage of both the analytical method and the numerical method. An overall strategy and make a simulation with the range data is given in the paper. The result is in agreement with the theoretical analysis and suggests that this strategy have a practical prospect.
LINE-OF-SIGHT GUIDANCE FOR ADHESION ASTEROID
CUI Hutao, SHI Xueyan, CUI Pingyuan, LI Aoshuang
2002, 22(3): 256-260.
Abstract(1862) PDF 410KB(1014)
Abstract:
A guidance and control strategy for attaching a vehicle to a small solar system body is presented. In order to ensure soft-landing, a prescribed line of sight and angle of sight profile satisfying restriction are planned, a sliding mode controller is designed to track the prescribed line of sight and angle of sight profile for safely soft-landing on surface of small asteroid. The robust feature of the close-loop guidance scheme is stressed. Finally, numerical simulations are conducted to verify that the given guidance and control strategy is feasible.
NUMERICAL INVESTIGATIONS OF A SMALL THRUSTER PLUME AT HIGH ALTITUDE
CHENG Xiaoli, MAO Mingfang, YAN Xiqin
2002, 22(3): 261-267.
Abstract(1882) PDF 638KB(1184)
Abstract:
A small thruster plume flow of nitrogen at high altitude is numerically investigated by using a DSMC method. A hard sphere model is employed to simulate nitrogen molecule. The collision frequency is calculated through using the random sampling frequency method for each cell. An axisymmetrc model based on a two-dimensional modification is introduced to model the flow field. To raise the computation efficiency of the DSMC method, both a grid domain decomposition method and a local grid clustering technique are enforced. An inner flow numerical result is considered as the outflow conditions of the thruster, a escaping boundary condition is implemented at far-field boundary, and a perfect scatter reflection model is chosen as the solid wall boundary condition. Moreover, molecule rotation energy included in inner energy is considered besides translation energy. The reliability of the numerical method is demonstrated by comparing with the relevant experimental results. Both the properties of plume flow at high altitude and the nonequilibrium effect related to rarefied gases are analyzed.Resultsshow that the DSMC method coupled with a fine grid technique is an effective approach for high altitude plume simulations, and that the nonequilibrium effect of gases must be numerically dealt with. Moreover, pitot pressures are given numerially in good agreement with measured data.
A METHOD FOR PROCESSING SEU DATA
HUANG Jianguo, HAN Jianwei, LIN Yunlong, HUANG Zhi, LU Xiuqin, ZHANG Xin, FU Zhangbo, GUO Jiyu, ZHAO Kui
2002, 22(3): 268-274.
Abstract(2192) PDF 686KB(1067)
Abstract:
Recently we carried out SEU measurements of some devices in a heavy ion accelerator. Because the ions with higher LET values don't have larger ranges in Silicon, when they are used to probe a device with thick die layer, they are either not able to reach the sensitive volume, or deposit very limited energy in the sensitive volume even though they reach there, as a result, the measured σ-LET curve greatly deviates from weibull function. These kinds of data are usually regarded as unsatisfactory and discarded. In fact, these data may contain very important physical information, and if processed properly, can provide some key parameters about the sensitive volume. To introduce the suggested data processing method, the SEU data for IDT7164 is processed as an example, from which such key parameters as the die layer thickness, the sensitive volume thickness, as well as the threshold of deposited energy for upset are extracted, which are well in agreement with abroad measured results. These parameters are not only very important for SEU sensitivity evaluation of onboard devices, but also difficult to acquire through other experimental methods. Finally, based on the introduced method, some preliminary thoughts are put forward about how to use combination of ions with large and short ranges to probe the key parameters about sensitive volume of a device. Furthermore, how to select proper combination of ions according to the characteristics of different domestic accelerators is discussed.
RESEARCH ON THE PROGRAM RELOADING IN THE MICRO-SATELLITE DESIGN
ZHOU Jian, DUAN Dengping, WANG Jianyu
2002, 22(3): 275-281.
Abstract(1999) PDF 598KB(1025)
Abstract:
The difference of the development of modern micro-satellite from traditional large satellites is the introduction of the integration conception. The integrated design conception of the micro-satellite make the program reloading on-board form the trend in the development of small satellite. Based on the conception of modularization and standardization, a method for program reloading in the micro-satellite is proposed and discussed in detail to meet the requirement of the micro-satellite design principle in this paper. The discussion is based on the CCSDS telemetry and telecommand scheme and distributed system on board connected with CAN bus. Some extension of the CAN protocol is involved to distinguish the normal data and program data when the node is receiving bytes from the bus. And some additional processes ensure the program data's security and precision. This method can be developed for system bootloading or just for error handling and system re-construction on-board. It will have wide application in the future.
ON THE DEPLOYMENT OF TETHERED SATELLITE SYSTEMS FROM A CIRCULAR OR ELLIPTICAL ORBIT
GU Xiaoqin
2002, 22(3): 282-288.
Abstract(1668) PDF 564KB(1068)
Abstract:
This paper investigates the ejection of tethered satellite systems. For the deployment of a tethered satellite from an elliptical orbit, the initial angle and velocity of the ejection that minimizes final errors are evaluated, and the dynamic equations are simplified with variable transformation. The method of orbital transfer is utilized for the deployment of a tethered satellite from a circular orbit. The parameters of orbit transformation are given, and the true anomaly is calculated at the end of transforming orbit. In many literatures, it is supposed that the mass of the spacecraft is far greater than that of the payload, so it is further supposed that the center of mass of the tethered satellite system coincides with that of the spacecraft. Those assumptions are only correct for that the spacecraft is massive, such as a space shuttle or a space station. In this paper, there is no assumption that the mass of the spacecraft is far greater than that of the payload, so the conclusions are more general. The numerical simulation results are presented and show that the method is really effective.