空间科学学报

Abstract:
The Wang-Sheeley-Arge (WSA) model is an empirical model that can predict the background solar wind speed and Interplanetary Magnetic Field (IMF) polarity on the Earth. It utilizes the line-of-sight synoptic solar magnetograms as input to give predictions about 3 to 4 days in advance. It is an improved version of the original Wang and Sheeley (WS) model. The relationship was generalized according to the parameters of the Coronal Hole Boundary (DCHB) model. The solar wind velocity is first determined at a certain height by the expansion factor of the magnetic field and the minimum angular distance that an open field footpoint lies from nearest coronal hole boundary. And then a simple 1-D modified kinematic model (1-DMK), which includes an ad hoc method to account for stream interactions, is used to transport the wind from the corona out to the Earth. In the course of development, the WSA model has been improved gradually in the details, such as the source of synoptic magnetograms, the type of coronal magnetic field model, the values of free parameters in velocity relation, the way of mapping the solar wind to earth and so on. Many studies were devoted to improve the prediction accuracy of the WSA model, and it is widely used now in many Magnetohydrodynamic (MHD) solar wind model.

Characteristic Times and Longitudinal Distributions of Gradual Solar Energetic Particle Events

DING Liuguan, CAO Xinxin, WANG Zhiwei, GU Bin

2018, 38(3): 296-306. doi: 10.11728/cjss2018.03.296

Abstract(1026) PDF 4751KB(359)

Abstract:
The two characteristic times (onset time t_ob and release time t_sr) and their longitudinal distribution of 30 gradual Solar Energetic Particle (SEP) events from 2011 to 2014, which particle flux increase remarkably in a short time, are analyzed. The results show that the SEP events observed by multi-spacecraft are usually associated with the wider halo Coronal Mass Ejection (CME) than those of general SEP events. The onset time difference of energetic particles observed by two spacecraft presents a good linear correlation with the longitude difference of two spacecraft, and east-west hemispheric asymmetry. The time intervals between the onset and release time and the flare onset are positively correlated with the relative longitude of the detector to the active region. The range of onset time or release time (t_slow-t_fast) in different energy channels for one SEP event shows a good positive correlation with the relative longitude of spacecraft, and release time ranges in different energy channels have a distinct longitudinal distribution. The release time interval between high and low energy channel has a positive correlation with CME speed. Therefore, the two characteristic times, in-situ onset time and solar particle release time near the sun, have obvious longitudinal distributions, and a strong correlation with the associated CME.

Deflection of Magnetopause in the Distant Magnetotail

SHANG Wensai, LÜ Jianyong, WANG Ming, NI Sulan

2018, 38(3): 307-314. doi: 10.11728/cjss2018.03.307

Abstract(1188) PDF 4043KB(2990)

Abstract:
The responses of the magnetopause in the distant magnetotail to the interplanetary and solar wind conditions, especially to the variation of the solar wind velocity, are studied by WIND and ARTEMIS data. It is found that the properties of sustaining dense high-speed flow were observed by P2 satellite in the magnetosphere on 13 September 2011, which suggests that the satellite passed through the magnetopause and entered the magnetosheath region. The data are analyzed using the minimum variable method. The results show that the normal of the magnetopause is along the direction of the solar wind velocity. According to the similar triangular theorem, it can be deduced that the deflection scale of the magnetopause is about 10R_e and 6R_e in y and z direction respectively. And the relative position of the P1 and P2 satellites also confirmed this opinion. The analyses suggest that the magnetopause location and shape in this event are mainly affected by the solar wind speed in the distant magnetotail. The result can provide observational evidence for establishing the magnetopause model which includes the effects of the solar wind v_y and v_z.

Tailward Expansion of the Plasma Sheet during a Substorm Using THEMIS Observations

REN Nian, SHEN Chao, MA Yonghui

2018, 38(3): 315-331. doi: 10.11728/cjss2018.03.315

Abstract(1175) PDF 8631KB(3075)

Abstract:
A moderately intense substorm from 10:40UT to 12:10UT on 13 March 2008 observed by THEMIS probes is examined to analyze the global evolution of the substorm in the magnetotail. During this substorm, five THEMIS probes are arranged along the x-axis in the vicinity of the midnight, from the radical distance of about 8.7 to 13.2R_e. Magnetic field dipolarization and plasma sheet expansions are all observed by different probes after the substorm onset. The average velocity of the plasma sheet expansions is about 140km·s^-1. Two types of dipolarization are detected in this substorm. One type is dipolarization front which is associated with the Bursty Bulk Flow (BBF). The other type is global dipolarization which is associated with plasma sheet expansions.The occurrence of Pi2 pulsation can be observed at low, medium and high latitudes 7 minutes later from the substrom onset. The amplitude of Pi2 pulsation gradually increases with the increase of latitude. The ion bulk velocity in the substorm event is mainly caused by the ion drift velocity, and the measured electric field is the induced electric field generated by the change of the local magnetic flux.

Gyroresonance between Fast Magnetosonic Waves and Particles in a Multi-ion Space Plasma

XIAO Hui, ZHOU Qinghua

2018, 38(3): 332-341. doi: 10.11728/cjss2018.03.332

Abstract(1950) PDF 4081KB(4324)

Abstract:
Fast Magnetosonic (MS) waves are right-hand polarized waves. They propagate both inside and outside the plasmasphere, and the wave vectors are almost perpendicular to the ambient magnetic field. Fast MS waves can lead to local electron acceleration, scattering of outer radiation belt energetic electrons, and scattering of energetic protons etc. Using the fully and high-density approximated dispersion relations, the dispersion curve of fast MS with different wave normal angle is analyzed, and the minimum resonant energy between MS waves and ions (H⁺, He⁺, and O⁺) are calculated. The results show that, as the wave normal angle is relatively small, the minimum resonant energy obtained by the high-density approximated and fully dispersion relation is quite close to each other in a high density and weak magnetic field space plasma. Remarkable error occurs when the high-density approximated dispersion relation is used in the low and medium density space plasma or when the wave normal angle is greater than 88°. Therefore, the fully dispersion relation must be used in these cases.

Case Study of Meteoroid Producing Long-duration Meteor Trail Irregularity

LI Ao, LI Guozhu, NING Baiqi, YANG Sipeng, WAN Weixing

2018, 38(3): 342-350. doi: 10.11728/cjss2018.03.342

Abstract(1122) PDF 6385KB(316)

Abstract:
Meteoroids enter the Earth's atmosphere, creating columns of ionization and leaving a meteor trail of dense plasma, and the meteor irregularities are often produced through plasma instability. Using the simultaneous observations of meteor and meteor trail irregularities obtained by optical video and VHF radar over low latitude Sanya, respectively, a method to derive the characteristics of meteoroid producing meteor trail irregularities is developed. A case of long duration meteor trail irregularities observed during the Geminid meteor shower in December 2015 is investigated. The velocity, mass and orbit parameters of meteoroid are estimated through the location information of the meteor trail irregularities detected by radar and the direction and gray information of meteor trajectory observed by optical video. The results show that the speed and orbital parameters of the meteoroid producing the long-duration case are similar to those of the parent meteoroid causing the Geminid meteor shower. The method is expected to help understanding the occurrence characteristics of meteor trail irregularities and their corresponding meteoroids.

Analysis of Ionospheric Scintillation Spectra Characteristics in Guangzhou Region

FAN Xiaobang, HUANG Jiang, XU Jie, DENG Baichang, QUAN Hongjun

2018, 38(3): 351-360. doi: 10.11728/cjss2018.03.351

Abstract(1089) PDF 4192KB(520)

Abstract:
Based on the data of GPS ionospheric scintillation observed at Guangzhou region in 2014 and 2015, 4820 scintillation spectra and spectral indexes are extracted from 150 typical flicker events. The analyses find that there are mainly two types of scintillation spectra in Guangzhou region, which can be subdivided into five categories. The characteristics and causes of typical scintillation spectrum are analyzed. The study found that the spectral index are from 0.63 to 9.57, and the average spectral index is 3.86. More than 78.5% of the spectral indexes are distributed from 0 to 6. 83.4% of weak scintillation intensity spectral indexes are distributed from 0 to 7, and 89.27% of strong flashing spectral indexes are distributed from 5 to 10. The spectral index increases as the flicker index increasing.

Comparison between Temperature Data of TIMED/SABER and AURA/MLS

XIE Yanxin, XIAO Cunying, HU Xiong, WU Xiaocheng, YANG Junfeng

2018, 38(3): 361-367. doi: 10.11728/cjss2018.03.361

Abstract(1386) PDF 3198KB(569)

Abstract:
Atmospheric temperature data from 20 to 90km height measured by AURA/MLS is compared with those measured by TIMED/SABER. The absolute temperature deviation between AURA/MLS data and TIMED/SABER data is calculated, and the feature of the average temperature deviation with latitude, longitude and altitude is analyzed. The results show that the average temperature deviation from 20 to 80km is smaller than ±6K, and the relative deviation is smaller than 3%. The average temperature deviation from 80 to 92km decreases to -10K, and the corresponding relative deviation is smaller than 9%. The variation tendency of average temperature deviation at mid and low latitude has almost the same trend. The deviation at 20km is -3K, and it increases gradually to a positive peak of 3K at 45~50km. The average temperature deviation varies obviously with latitude, while varies very less with longitude. The results are of interest for satellite data application.

Analysis of Condensation Heat Transfer in Curved Triangle Microchannel under Microgravity

LEI Yuchuan, CHEN Zhenqian

2018, 38(3): 368-372. doi: 10.11728/cjss2018.03.368

Abstract(1119) PDF 2249KB(3080)

Abstract:
Numerical simulations of condensation heat transfer in triangle microchannels are presented. The model is established on the Volume of Fluid (VOF) approach and the user-defined routines which includes heat transfer at the vapor-liquid interface and latent heat. The predictive accuracy of the numerical model is assessed by comparing the heat transfer coefficient with the available empirical correlations in the literature. The influence of gravity and surface tension on the liquid-vapor interface distribution and heat transfer performance are analyzed. No obvious effect of the gravity is observed in the liquid-vapor interface distribution and the average cross sectional heat transfer coefficient. Surface tension, which plays a dominate role during the condensation in non-circular microchannels, leading to reduction of the condensate film thickness at the sides of the channel and accumulation of the condensate at the corners of the channel, giving rise to smaller thermal resistance and better heat transfer performance.

Transition Process of Supercritical Thermocapillary Convection in a Shallow Annular Pool for Low Prandtl Number Fluids

ZHANG Li, LI Yourong, LIU Lina, WU Chunmei

2018, 38(3): 373-379. doi: 10.11728/cjss2018.03.373

Abstract(963) PDF 4436KB(2537)

Abstract:
In order to understand the transition process of thermocapillary convection of low Prandtl number (Pr) fluids, a series of three-dimensional numerical simulations on thermocapillary convection of Pr=0.011 fluid in a shallow annular pool are performed. Results indicate that the flow is axisymmetric steady flow at a small Marangoni number. When Marangoni number exceeds a critical value, the flow destabilizes and bifurcates to the hydrothermal wave. In this case, the wave number decreases and the fundamental frequency increases with the increase of Marangoni number. When Marangoni number continue increasing, the hydrothermal waves are enhanced and bifurcated to the radial waves. During this transition, there exists a sharp drop of the wave number. Finally, the noise on frequency spectrum increases and behaves in multi-frequencies. Therefore, the bifurcation route of thermocapillary convection is from axisymmetric steady flow, hydrothermal wave, radial waves with one frequency to three-dimensional oscillatory flow with multi-frequencies.

Application of Metal Additive Manufacturing Technology for Space

LIU Yifei, LI Liang, WANG Gong, LIU Bingshan

2018, 38(3): 380-385. doi: 10.11728/cjss2018.03.380

Abstract(1372) PDF 2663KB(636)

Abstract:
In the high energy beam metal additive manufacturing technology, the laser and electron beam are used as the heating source to realize the manufacture of metal parts by powder melting or fuse deposition modeling. Based on the development of the metal additive manufacturing technology in the field of space, combining with the higher requirements of the on-orbit equipment size, weight, power consumption and life span induced by the strong constraints of space station and deep space exploration, the two working modes of the laser and electron beam heating sources are compared,and the on-orbit feasibility is analyzed. Moreover, the problems as well as the solutions to the development of future space metal additive manufacturing technology are presented.

Data Correction Method of Electric Field Instrument Onboard Spin Platform

YANG Xuan, ZHOU Bin, WENG Chenghan

2018, 38(3): 386-392. doi: 10.11728/cjss2018.03.386

Abstract(1024) PDF 2016KB(311)

Abstract:
The double-probe Electric Field Instrument (EFI) is a common instrument used in the space electric field detection. The space electric field can be calculated according to the potential difference and the distance between two probes. In practical work, the wire boom of EFI onboard the spin platform may get position disturbances, which may influence the calculation in distance and numeric values of the electric field. In this paper the double-probe EFI and its working principle are introduced, meanwhile the self-correction method with the processed data of single probe to revise the double probes detection results on a spin platform is illustrated. After eliminating the interference of the platform, the data from the space experiment in sounding rocket is processed with the method introduced in this paper, and the magnitude and direction of measured electric field vectors are corrected. Finally, the correction results are compared with the uncorrected data and the theoretical data to verify the validity of the correction method.

Error Analysis of Generation and Detection of Electromagnetic Vortex Using Uniform Circular Array

CHEN Yanan, DONG Xiaolong

2018, 38(3): 393-401. doi: 10.11728/cjss2018.03.393

Abstract(1064) PDF 4296KB(623)

Abstract:
For realization of multiplexing of electromagnetic vortex, error performance of generating and detecting electromagnetic vortex by uniform circular array is analyzed. When generating electromagnetic vortex by the uniform circular array, there exists different excitation phase errors including Gaussian distribution error, quantified error, single element error et al. The electromagnetic vortex amplitude-phase characteristics are simulated and analyzed under these phase errors, then the orbital angular momentum modes are calculated, and the error thresholds are given when the modes can be accurately identified. At the same time, the amplitude-phase distribution is analyzed when the detecting array is not parallel to the generation array. Simulation results show that the magnitude of the electromagnetic vortex will become irregular and the phase will remain well within the width of the main lobe under various generating phase errors, and the orbital angular momentum mode cannot be recognized even under small inclination angle detecting error. The results indicate that the electromagnetic vortex has good anti-interference performance for these generating phase errors. However, it is highly sensitive to the inclination angle detecting error.

Autonomous Navigation Scheme of LEO Constellation Based on Inter-satellite Link and Magnetic Field

TAN Longyu, WANG Weihua, SUN Jun, HAN Fei, PENG Yang, WANG Zhaolong

2018, 38(3): 402-408. doi: 10.11728/cjss2018.03.402

Abstract(1345) PDF 2008KB(495)

Abstract:
Compared to autonomous navigation of Low Earth Orbit (LEO) constellation based on inter-satellite link only, a method for autonomous navigation of LEO constellation combining inter-satellite link and geomagnetic measurement is proposed to solve the problem about overall rotation and drifting of LEO constellation. The absolute property of geomagnetic field is fully utilized. Spatial reference information is provided for LEO constellation by obtaining and analyzing the angular distance between the line-of-sight vectors of adjacent satellites in the same orbit of the LEO constellation, as well as the direction and module value of geomagnetic field. After non-rank deficient analysis, the state equation and measurement equation are established. The optimal estimation about the whole state of LEO constellation can be realized using Extended Kalman Filtering (EKF). The simulation results demonstrate that the position error is less than 20m and velocity error is less than 0.05m·s^-1. The autonomous navigation of LEO constellation can last 180 days, which meets the application requirements.

Thermal Design and Simulation of a Space Phase Change Heat Exchanger

MA Caixin, SHENG Qiang, TONG Tiefeng

2018, 38(3): 409-417. doi: 10.11728/cjss2018.03.409

Abstract(1563) PDF 3773KB(3506)

Abstract:
Phase Change Material (PCM) is widely used in energy storage due to its huge latent heat. To overcome its drawback of poor thermal conductivity, a Phase Change Heat Exchangers (PCHE) which combine the advantage of heat exchanger and PCM is designed. It can be used cooling high density of heat flow rate surface in aero-space. Based on the phase change computing methods-Enthalpy method for solidification and melting model, the numerical simulation of a kind of plate PCHE, which used water and paraffin as cooling medium and phase-change material, is studied. The transient temperature distribution, solid-liquid phase interface changes and melting time are obtained under different gravity conditions. The results show the performances of PCHE satisfy the design request. comparing the results under different gravity conditions, Heat Transfer Enhancement Method (HTEM) is used by add fins and metal or ceramic foams to improve the efficiency of the PCHE under microgravity. It is valuable to the design and experiment research of space PCHE.

Construction of Regional Point Mass Model in Polar Regions

FENG Jinkai, WANG Qingbin, HUANG Jiaxi, ZHANG Chao, FAN Diao

2018, 38(3): 418-426. doi: 10.11728/cjss2018.03.418

Abstract(892) PDF 4597KB(2860)

Abstract:
In the traditional polar coordinate system, the latitude and longitude grids will undergo serious deformation in the polar regions. This deformation will cause the design matrix of point-mass model equation unsolvable, and the spherical harmonic method is singular near the two polar points. In this paper, the singularity problem in the calculation of disturbing gravity and the instability problem during the construction of point mass model in polar regions is studied. The singularity elimination algorithm is introduced in spherical harmonic method and the construction of point mass model based on pole transform is proposed. Numerical experiment results show that the singularity elimination algorithm can effectively solve the singularity problem near the poles, and the structure of point mass model based on the pole transform method is stable and the model can achieve the same accuracy compared with the traditional one, which provides a new way for disturbing gravity fast calculation of polar region aircraft.

“黄金时间”搞科研必有更大作为——量子科学实验卫星首席科学家潘建伟访谈

2018, 38(3): 427-427.

Abstract(487) PDF 1966KB(314)

Abstract:

中国科学院微重力重点实验室

2018, 38(3): 428-428.

Abstract(709) PDF 681KB(300)

Abstract:

2018 Vol. 38, No. 3

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