空间科学学报

2000 Vol. 20, No. 4

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PROPAGATION OF DISTURBANCES IN SOLAR CHROMOSPHERE-CORONA

LI Bo, WANG Shui

2000, 20(4): 289-296. doi: 10.11728/cjss2000.04.289

Abstract(1764) PDF 456KB(639)

Abstract:
In order to simulate the propagation characteristics of disturbances in solar chromosphere, transition layer and corona, we discuss numerically the propagation process of a disturbance produced by local heating in vicinity of transition layer, by adopting a 2-dimensional MHD simulation under a self-consistent non-isothermal, non-uniform initial state. The results indicate that the disturbance propagates to ambient plasma with a speed of local fast MHD wave. We find the numerical results can fit in with that computed via local fast MHD wave, its characteristics can explain wave events observed by SOHO/EIT.

EFFECTS OF THE INTENSITY OF MAGNETIC FIELD ON THE STEADY CORONAL STRUCTURE

LI Jingqun, WEI Fengsi

2000, 20(4): 297-302. doi: 10.11728/cjss2000.04.297

Abstract(2020) PDF 358KB(1012)

Abstract:
Based on the 2-D MHD model and time relaxation method, using the pro- jective characteristic boundary conditions on the inner and outer boundaries, the effects of the magnetic field intensity on the steady coronal structures are investigated. The simulation results show that with the increasing dipolar magnetic field, the constraint of the magnetic field on the solar wind is strengthened, the degree of opening of the close magnetic field in the lower latitude decreases, the velocity difference between the higher latitude and the lower latitude increases, taking maximum near the point where Alfvenic mach number is 1, and the velocity transition region is steepened. On the other hand, with the increasing heliospheric distance, the velocity transition region is also steepened. The result can be used to qualitatively explain the Ulysses observations in the region far from the sun.

LIMB-DARKENING EFFECTS OF STELLAR ANGULAR DIAMETER MEASUREMENT

ZHAO Dingfeng, HANG Hengrong, CHEN Zidong

2000, 20(4): 303-309. doi: 10.11728/cjss2000.04.303

Abstract(2411) PDF 411KB(948)

Abstract:
In this paper the influence of the limb-darkening effects on stellar angular diameter measurement were studied. It shows that both UD and linear results underestimate the value of angular diameter; the difference is larger at stronger limb-darkening effects (c0 - 0), the largest difference among UD, linear result and quadric approach are 25.5%, 12.6% respectively. While their differences can be ignored when co tended to one. However, the difference between new and old linear approach seems small, it thinks that the quadric limb-darkening effects should be considered in the measurement of the stellar angular diameter.

PREDICTING THE MONTHLY MEAN VALUES OF f₀F₂ BY USING THEARTIFICIAL NEURAL NETWORK

LIU Wen, JIAO Peinan

2000, 20(4): 310-317. doi: 10.11728/cjss2000.04.310

Abstract(2290) PDF 519KB(1112)

Abstract:
A method to predict the monthly mean Values of f₀F₂ is presented in this paper. The analysis results of monthly values of f₀F₂ indicate that the characteristic of this ionospheric parameter change with different month and different year. Based on it, the f₀F₂ monthly mean value is predicted by taking sufficient data of many yeas into account and improved the predicting method. Compared with the conserved data, the average error is less than 0.34MHz. Then, the fraction characteristic of ionosphere has been set forth by using the theory of fraction and the fraction dimension of the f₀F₂ monthly mean value has been acquired. Based on it, 3 parameters are selected to predict the f₀F₂ monthly mean value for different year, thus, the predicted technology is improved further. Compared with the conserved data, the average error is less than 0.3 MHz.

THE LARGE NIGHTTIME INCREASE IN IONOSPHERIC HEIGHTS AT WUHAN DURING THESTORM OF APRIL 2000

LIU Libo, WAN Weixing, YUAN Hong, NING Baiqi, GAO Yufen

2000, 20(4): 318-322. doi: 10.11728/cjss2000.04.318

Abstract(2147) PDF 332KB(905)

Abstract:
A great geomagnetic storm occurred around 1640 UT on April 6, 2000, with a Value of -317nT in Dst index. The responses of the ionosphere at Wuhan during the first stage of this storm were reported in this paper. Soon after the sudden storm commencement (SSC) at 1640 UT, the main phase of the geomagnetic storm appeared, and the storm stepped into its recovery phase at the beginning of the next day. A rapid and large increase in the ionospheric heights at Wuhan occurred at the beginning of the main phase, and the lifts in h'F and h_mF₂ lasted for about 2 hours. The value of f₀F₂ decreased about 1.6 MHz at the beginning of the main phase, and the maximum value of f₀F₂ on the next day was less than that on April 5 more than 3 MHz at Wuhan. The almost simultaneous increase in h'F was also observed at Chungli, Taiwan. The near simultaneity of the h'F disturbances at the two stations suggested that an E x B plasma drift due to an east-west electric field of storm origin was the cause of the rapid and large lifts in the nighttime ionospheric heights after the SSC.

THE STATISTICAL DISPERSION CHARACTERISTICS OF MEDIUM-SCALE TRAVELINGIONOSPHERIC DISTURBANCES OBSERVED AT MILLSTONE HILL

YUAN Hong, WAN Weixing, LIANG Jun, DING Feng

2000, 20(4): 323-327. doi: 10.11728/cjss2000.04.323

Abstract(1929) PDF 322KB(609)

Abstract:
The dispersion character of medium-scale Travelling Ionospheric Disturbances (TIDs) observed at Millstone Hill (288.5°E, 42.6°N) is statistically studied. The result shows that, on frequency-velocity plane, there exist several peaks of TIDs occurrences. Further analysis shows that the observed dispersion characteristics matches the theoretical dispersion relations of guided gravity waves. That is to say some high frequency TIDs, may be interpreted as the fully guided waves between the ground and the bottom of thermsphere, and the low frequency TIDs may be related to guided waves L₁, W₁ and W₄.

STUDY ON THE TL SENSITIVITY, SHOCKING PHASE AND K CONTENT OF TEN HCHONDRITES

LIU Jingfa, PEN Jinlian, YU Chiling, LI Dahong

2000, 20(4): 328-332. doi: 10.11728/cjss2000.04.328

Abstract(2377) PDF 356KB(854)

Abstract:
The thermoluminescence (TL) sensitivityg TL peak temperature, peak halfwidth temperature and potassium (K) content of 10 H chondrites (fell in China) have been measured in this paper. Through comparing the TL sensitivity and K content with the shocking phase, it is found that there is a relationship of the TL sensitivity and K content with the shocking phase.

EFFECTS OF TRACK STRUCTURE OF HIGH-ENERGY HEAVY IONS ON SINGLE EVENT UPSET

HAN Jianwei

2000, 20(4): 333-339. doi: 10.11728/cjss2000.04.333

Abstract(2265) PDF 425KB(979)

Abstract:
The track structure of high-energy heavy ions was calculated in this paper and using Monte Carlo method, effects of the track structure on single event upset was studied. Taking into account the track structure, devices with small sensitive cell and low upset threshold show lower upset cross sections and upset rates, when compared with LET calculation. When ion becomes heavier, this decrease is remarkable even for devices with moderate dimension sensitive cell and higher upset threshold. In general, ion track shows effect when effective deposited energy is comparable with upset threshold. High-energy heavy ions can penetrate into thick material, in addition large dimensional track has chance to deposit enough energy in neighboring cells simultaneously. Both of these two cases can give rise to multiple-bit upsets. And this multiple-bit upsets effect can't be calculated with LET.

EXPERIMENTAL INVESTIGATION OF GAS-LIQUID TWO-PHASE FLOW UTILIZINGREDUCED GRAVITY AIRPLANE

ZHAO Jianfu, LIN Hai, XIE Jingchang, HU Wenrui, LU Congmin, ZHANG Yuhan

2000, 20(4): 340-347. doi: 10.11728/cjss2000.04.340

Abstract(2411) PDF 530KB(961)

Abstract:
An experimental investigation of the air-water two-phase flow in a tube with a12mm×12mm square cross-section is performed under reduced gravity on board IL-76MDK Russian airplane. Three main flow patterns of the gas-liquid two-phase flow under reduced gravity conditions are observed. The flow rates of the air and water phases, the water temperature and the pressure inside the test section are obtained. The flow pattern transitional criteria of the gas-liquid two-phase flow at reduced gravity are also discussed.

ADAPTIVE CONTROL FOR SPACE MANIPULATOR TO TRACK THE DESIRED TRAJECTORYIN JOINT SPACE

CHEN Li, LIU Yanzhu

2000, 20(4): 348-355. doi: 10.11728/cjss2000.04.348

Abstract(2576) PDF 465KB(1371)

Abstract:
In this paper, the dynamics and control problems of free-floating space manip- ulator systems are studied. It is verified that the dynamic equations of free-floating space manipulator systems can be linearly dependent on a group of inertial parameters. Based on the results and with the augmentation approach, an adaptive control scheme for space manipulator systems with unknown payload parameters to track the desired trajectory in joint space is developed. The control scheme proposed above is structurally and computationally simple, because of an effective exploitation of the system dynamics. In particular, it requires not the measuring of the position, velocity and acceleration of the base. A simulation study of two-link planar space manipulator system is presented; it is shown that the control scheme proposed is feasible and effective.

OPTIMAL DESIGN FOR STRUCTURAL LOCK OF SPATIAL DOCKING MECHANISM

WU Yizhong, LIU Zhiquan, CHEN Liping, ZHOU Ji

2000, 20(4): 356-365. doi: 10.11728/cjss2000.04.356

Abstract(2427) PDF 430KB(1242)

Abstract:
Structural lock is an electromechanical equipment that connects rigidly two space shuttles together. In this paper, the eccentric wheel plus cam mechanism scheme is selected. Based on analyzing their advantages and disadvantages, it is pointed out that this structure is simple and self-locking is reliable. Then the parameter of turning and pulling process are optimized. The optimization of structural lock during the pulling process is discusses in view of minimum torsion, minimum power and minimum time. It has been proved that the scheme optimized consumes least energy.

STUDY ON PARAMETER OPTIMIZATION OF ELECTROMAGNETIC BRAKE IN SPACEDOCKING MECHANISMS

ZHAO Yang, CAO Xibin, XU Yuru

2000, 20(4): 366-372. doi: 10.11728/cjss2000.04.366

Abstract(2387) PDF 396KB(961)

Abstract:
Electromagnetism brake was used as damper in androgynous and peripheral docking mechanisms by the USSR, which has successfully accomplished the mission of docking for many times. But only qualitative analyses were made in current references and there is no criteria sufficient for designing. In the paper, a moment model of electromagnetic brake is built, and parameter optimization designing of the brake is studied.

COMPARISON AND INVESTIGATION OF Es OCCURRENCE OF THE IONOSPHEREOVER CHONGQING AND LANZHOU

TAN Hui

2000, 20(4): 373-379. doi: 10.11728/cjss2000.04.373

Abstract(2167) PDF 429KB(968)

Abstract:
In this paper, Es occurrence and f₀E over Chongqing (29.5°N, 106.6°E) and Lanzhou (36°N, 103.9°E) are compared and studied. The results show that: (1) Change pattern of Es occurrence over these two stations has certain rules. During the daytime, Es occurrence over Chongqing is higher than that over Lanzhou, but at night the result is just the opposite. (2) Change of Es occurrence is consistent to that of the ambient ionization density. (3) Besides the difference of latitude of the two stations, it seems that the mechanism of the above characteristic is closely related to the S_q current systems.