Table of Content

    15 March 2019, Volume 39 Issue 2 Previous Issue    Next Issue
    90°Pitch Angle Enhancements of Suprathermal Electrons Associated with the Interplanetary Shock on 24 April 2008
    KONG Fanjing, QIN Gang
    2019, 39 (2):  143-148.  doi: 10.11728/cjss2019.02.143
    Abstract ( 840 )   PDF (2292KB) ( 439 )   Save

    Using test particle simulations, the 90° pitch angle enhancements of suprathermal electrons associated with the interplanetary shock on 24 April 2008 observed by STEREO-A spacecraft have been studied. Firstly, the initial distribution function for each pitch angle channel is obtained by fitting the observed distribution at a given time before the shock arrival, and then the time-backward method is used to calculate the pitch angle distributions of suprathermal electrons downstream of the shock for a given energy channel. Due to the higher resonance frequency of suprathermal electrons, the turbulence spectrum includes the dissipation range in which low-energy electrons resonate. Three energy channels with central energies of 215.76 eV, 151.67 eV, and 106.63 eV are simulated. The results show that a peak of the pitch angle distributions downstream of the shock obtained for these energy channels appears near the 90° pitch angle. The enhancement at the 90° pitch angle is in good agreement with the observations. The resonance between suprathermal electrons and the turbulence dissipation range in the process of shock acceleration is suggested to play a crucial role in this phenomenon. A thorough study of the electric and magnetic field fluctuations at interplanetary shocks can provide a better understanding of the nature of 90° pitch angle enhancements of suprathemal electrons.

    References | Related Articles | Metrics
    Global MHD Results of Flux Transfer Events at the Dayside Magnetopause under High Solar Wind Speed
    CHEN Chen, HUANG Zhaohui, SUN Tianran, TANG Binbin, WANG Chi
    2019, 39 (2):  149-157.  doi: 10.11728/cjss2019.02.149
    Abstract ( 924 )   PDF (4204KB) ( 427 )   Save

    Using Global MHD model, the spatial distribution of Flux Transfer Events (FTE) at the dayside magnetopause under high solar wind speed is investigated. The solar wind conditions of this case are vsw=1200 km·s-1, nsw=3 cm-3, Bz=-8.3 nT, By=8.3 nT and Bx=0 nT. The simulation results virtually agree with those expected FTE signatures from observations, and bipolar signatures and related variations of number density, pressure and velocity are found. A total number of 39 FTE are observed by ten virtual probes which are spread over the magnetopause from y=-5Re to y=5Re. 14 FTE are found when the probe is near to the noon. However, when the probe is located near y=-5Re and y=5Re, the same number, 3, of FTE in both locations is found. Furthermore, 8 FTE are found when the probe is adjacent to y=-2.5Re and 11 FTE are found near y=2.5Re. In a nutshell, the number of FTE decreases as the observed probes approach the flank of the magnetopause, which could be caused by the distribution of solar wind velocity in magnetosheath.

    References | Related Articles | Metrics
    Temporal and Spatial Characteristics of the Ionospheric Scintillation Event and the Influence on Communication in the Northern EIA Crest Region
    HUANG Linfeng, TIAN Pengju, ZHAO Kai, LIU Yun, YANG Juan, LIU Weifeng
    2019, 39 (2):  158-166.  doi: 10.11728/cjss2019.02.158
    Abstract ( 969 )   PDF (2453KB) ( 282 )   Save

    The temporal and spatial variations of the ionospheric scintillation event and the influence on communication are studied using GPS measurements at Shenzhen station (Geographic latitude 22.59°N, Geographic Longitude 113.97°E, Geomagnetic Latitude 12.58°N) of Chinese Meridian Project, situated under the northern crest of the equatorial anomaly region, during the period from January 2011 to December 2017. The results show that: GPS scintillation events were largely a nighttime phenomenon, and most of the scintillation events were observed in equinox months; during different solar activity, scintillation events were mainly occurred at the inner edge of the northern crest of equatorial anomaly in China, and scintillation events are more probable to be observed in the west sector of the sky above Shenzhen station; during different solar activity, the weak scintillation events were relatively less accompanied by the TEC depletions and loss of lock on GPS signals, however, most of the strong scintillation events are accompanied by the TEC depletions and loss of lock on GPS signals.

    References | Related Articles | Metrics
    Development of Agile Digital Ionosonde and Its Preliminary Observation
    LAN Jiaping, NING Baiqi, ZHU Zhengping, HU Lianhuan, SUN Wenjie, LI Guozhu
    2019, 39 (2):  167-177.  doi: 10.11728/cjss2019.02.167
    Abstract ( 858 )   PDF (4510KB) ( 260 )   Save

    Ionosonde, as one of the most important instruments for ionospheric observation, is usually deployed at permanent stations because of its large size antennas and main machine. Owing to the increasing spatial and temporal resolution requirements of ionosonde observations, the development trend of ionosonde is toward agile in field site setup and ionospheric disturbance detection. In recent years, some important achievements have been made in lowering the transmitting power and reducing the size of the main machine. However, it is still a standing technical issue to perform fast ionospheric sounding and produce high quality ionogram under small antennas and low transmitting power condition. In regards to this issue, based on the newly developed high speed digital circuits and RF devices, an agile digital ionosonde is designed and developed by using the narrow band tracking filtering, pulse compression, code multiplexing and antenna matching techniques. The agile digital ionosonde uses small transmitting and receiving antennas with several meters height and portable main machine. Its main characteristics include mobile observation, system parameters agility and fast ionospheric disturbance detecting. It is configured with arbitrary frequency sweeping vertical sounding, high Doppler resolution vertical sounding and oblique sounding observation mode. The observations performed at several stations in China indicate that the agile digital ionosonde can be well employed to make fast measurements with high quality ionogram and is suitable for permanent and temporary stations. The agile digital ionosonde will provide an important way to sense ionospheric temporal and spatial variations, especially the fast disturbance and its propagation in a large area.

    References | Related Articles | Metrics
    Thermospheric Wind over Chinese Yellow River Station and Tromso during Auroral Substorm
    WU Pengju, ZHANG Yange, AI Yong
    2019, 39 (2):  178-185.  doi: 10.11728/cjss2019.02.178
    Abstract ( 518 )   PDF (5150KB) ( 258 )   Save

    The wind detection for the middle and upper atmosphere is of great significance to the study of atmospheric physical processes. In the polar region, atmospheric structure changes more quickly. By the all-sky Fabry-Perot interferometer, the Doppler shift of the airglow can be detected to retrieve the wind velocity at the airglow layer. In this paper, the neutral wind is studied at the OI 557.7 nm oxygen-atom layer in the Arctic Yellow River Station and the Tromso Station during a substorm. The average wind velocity is about 100 m·s-1 in the lower thermosphere. Due to the geomagnetic distribution, the thermospheric wind velocity increases sharply in the polar region. Finally, considering ion drift data, the influence of ion drag and Joule heating on the neutral wind is discussed. The results show that auroral substorm would not only make the wind stronger in the lower thermosphere but also inhibit it. Moreover, the wind velocity is perpendicularly to the auroral arc generally.

    References | Related Articles | Metrics
    Retrieval Algorithm of Middle Atmospheric Temperature Using Rayleigh Lidar
    LIU Xing, YANG Guotao, WANG Jihong, DU Lifang, JIAO Jing, WANG Zelong, XUN Yuchang
    2019, 39 (2):  186-190.  doi: 10.11728/cjss2019.02.186
    Abstract ( 1085 )   PDF (910KB) ( 349 )   Save

    Rayleigh lidar is an important equipment to measure temperature of the mesosphere. It has the capacity for continuous detection with high spatial and temporal resolution. To take full advantage of the original data obtained by Rayleigh lidar, the conventional Chanin-Haunchecorne method is improved. The initial temperatures adopted by the improved algorithm are obtained by uniform search, and then the atmospheric temperature can be inversed. The Rayleigh lidar located in Yanqing, Beijing (40.3°N, 116.2°E) consists of a 589 nm channel and a 532 nm channel. The 589 nm channel is used for calculating atmospheric temperature, and the 532 nm channel is taken as the reference of the former. The initial temperatures are chosen at regular intervals from 150 to 250°K, and the temperature profiles and its corresponding density profiles from 60 km to 70 km altitude is retrieved with the 589 nm channel. The accurate temperature and the corresponding temperature profile can be obtained according to the reference density profile. This reversed temperature profile is compared with that of 532 nm channel. The results show that they have good agreement with each other. This improved algorithm takes full advantage of optical signals with poor signal-to-noise ratio, and improves the upper detection limit of atmospheric temperature with 589 nm channel from 60 km to 70 km. The method is reliable.

    References | Related Articles | Metrics
    Convective Boundary Layer and Entrainment Zone Thickness over Wuhan (30.5°N, 114.4°E) Observed by Lidar
    WANG Penghui, YI Fan
    2019, 39 (2):  191-199.  doi: 10.11728/cjss2019.02.191
    Abstract ( 997 )   PDF (3737KB) ( 318 )   Save

    Variations of the Convective Boundary Layer (CBL) height and Entrainment Zone Thickness (EZT) have been studied based on 532-nm polarization lidar measurements between January 2011 and December 2017 at Wuhan (30.5°N, 114.4°E), China. The 1-min backscatter ratio R profiles are retrieved using the backward iteration Fernald method. The hourly CBL height and EZT are determined with the variance method. The results indicate that the CBL height and the EZT over Wuhan have obvious seasonal variation. The average value of the maximum CBL height is 1.14, 1.25, 1.06, and 0.74 km in spring, summer, autumn and winter respectively, while the average EZT is 0.4, 0.51, 0.34, and 0.26 km in spring, summer, autumn and winter respectively. These characteristics have a clear-cut positive correlation with the land surface temperature in Wuhan.

    References | Related Articles | Metrics
    Analysis of Airborne Acoustic Wave Wind-metering of the Near Space
    GUO Ganggang, TU Cui, HU Xiong, WU Xiaocheng, WEI Feng, SONG Liang
    2019, 39 (2):  200-204.  doi: 10.11728/cjss2019.02.200
    Abstract ( 838 )   PDF (1058KB) ( 259 )   Save

    A new in-situ method for atmospheric wind detection of the Near Space is proposed in this paper. The time delay difference of acoustic wave propagation is used to measure the wind. The principle of this method is introduced. The source and accuracy of wind measurement error are analyzed. The frequency and propagation distance of the signal are selected, by analyzing the attenuation of acoustic waves at the height of the Near Space. And the accuracy of acoustic time delay estimation with different SNRs is simulated. The results show that the accuracy of wind measurement by this method can reach a high level of 0.2 m·s-1 at the height of 20~50 km with the propagation distance of 2~5 m, the distance measurement accuracy of 1 mm, the platform velocity measurement accuracy of 0.1 m·s-1, and SNR is more than -2 dB, and the time delay measurement precision is less than 1μs.

    References | Related Articles | Metrics
    Behaviors of Capillary Surfaces of Liquid Drops in Rounded Corners
    HAN Zhiyi, DUAN Li
    2019, 39 (2):  205-213.  doi: 10.11728/cjss2019.02.205
    Abstract ( 968 )   PDF (3022KB) ( 353 )   Save

    Containers with interior corners are applied in space fluid management extensively. It has lots of profound guiding significance for Space Fluid Management to research the interfacial behaviors of liquids in corners of containers in microgravity. Due to either design or fabrication problem, ideally sharp corner may not be achieved, but rather a somewhat rounded one. In this paper, theoretical analysis and numerical simulation are performed to research the behavior of liquid drops in rounded corners, including the case in which the contact angles on the two sides of the corner may be different, leading to a generalization of the Concus-Finn conjecture. Comparing with Concus-Finn conjecture which is a useful criterion to determine the behavior of liquid drops in sharp corners, there are some different characteristics of capillary surfaces behaviors in rounded corners. The generalized conjecture shows that the behaviors of capillary surfaces in rounded corners depend on not only the contact angle and the degree of interior corners, but also the radius of the rounded corners and the volume of liquid drops, which are dramatically different in sharp corners.

    References | Related Articles | Metrics
    Multispectral Full-disk Solar Extreme Ultraviolet Imager
    PENG Jilong, FENG Taojun, SHI Entao, LI Lin, YU Qian, ZHANG Kai, NIE Xiangyu, MA Ziliang
    2019, 39 (2):  214-221.  doi: 10.11728/cjss2019.02.214
    Abstract ( 948 )   PDF (3450KB) ( 316 )   Save

    Solar Extreme Ultraviolet (EUV) has violent variation during solar eruption. Solar EUV imagers are important data for solar activities evolution analyses. Solar EUV spectral information can be applied in high temperature coronal plasma research. But both the traditional solar EUV telescope and the slit spectrograph have their limitations. High spectral resolution and wide field-ofview cannot be simultaneously achieved by either the traditional EUV imager or the spectrometer. The design of a new type of solar EUV multispectral imager is introduced in this paper. The full-disk solar image with high spectral and spatial resolution can be obtained by a kind of slitless grating with a grazing incidence structure. The field-of-view of the imager can be as broad as 47'. The high spectral resolution is 2×10-3 nm per pixel and the spatial resolution is 1.4' per pixel. The temporal resolution of the full-disk is better than 60 s. The analysis of the full-disk spectral image and system response shows that the imager can observe the evolution of global solar activities, and can provide more comprehensive data for solar physics research and space weather forecast.

    References | Related Articles | Metrics
    Analysis for the Star-tensegrity Deployable Structure
    LUO Ani, LIU Heping
    2019, 39 (2):  222-227.  doi: 10.11728/cjss2019.02.222
    Abstract ( 926 )   PDF (2838KB) ( 299 )   Save

    A star-tensegrity deployable structure is presented. It is formed through transforming the star tensegrity structure and can be driven by a central member to complete folding and deploying. Firstly, based on the tensegrity unit, the star-tensegrity structure is presented and the scheme for the star-tensegrity deployable structure is investigated. Then how to drive it is discussed and determined. Finally, the influence of the central member length on the structural and force parameters is analyzed. Through theoretical analysis and simulation, the feasibility for folding and deploying of the star-tensegrity deployable structure is checked and verified. The results show that a feasible star-tensegrity deployable structure is obtained.

    References | Related Articles | Metrics
    Designing of Conical Surface Configuration for the Probe-cone Docking Mechanism Facing to Mini-Spacecraft
    HAN Wei, JIANG Zhijie, HUANG Yiyong, CHEN Xiaoqian
    2019, 39 (2):  228-232.  doi: 10.11728/cjss2019.02.228
    Abstract ( 566 )   PDF (1218KB) ( 304 )   Save

    With mankind ceaselessly breaking new ground in the field of space, the growing demands for autonomous on-orbit servicing are putting forward higher requirements to the autonomy, diversity, robustness, reliability and the overall performance of the space rendezvous and docking mechanism. To ensure high success rate and reliability of the spacecraft docking process in space, attentions should be paid on the design, development and test of the docking mechanism. Focusing on the probe-cone docking mechanism utilized on mini-spacecraft for On-Orbit Servicing (OOS), a new design objective of docking cone is presented in this paper. The impact process is simulated using the explicit finite element code, ANSYS/LS-DYNA, and the influence of the docking mechanism on the process is investigated with the kinematical simulation. In addition, on the basis of above simulation analyses, the innovational design technique of docking cone is studied and a new satisfied docking cone is obtained. The results show that the integrated performance of the whole mechanism can meet the capturing requirements of the design objective.

    References | Related Articles | Metrics
    Precision Thermal Control Scheme of Fluctuating Temperature for Space Fluid Loop
    ZHANG Hanze, ZHENG Tong, ZHANG Hanxun, CHEN Bo
    2019, 39 (2):  233-241.  doi: 10.11728/cjss2019.02.233
    Abstract ( 901 )   PDF (2917KB) ( 310 )   Save

    Fluid temperature at the inlet branches of the space fluid loop fluctuates randomly within a specific range, therefore measures should be taken to decrease their thermal effects on cold-plate cooled high-stability requirement payloads. Because the traditional patch heaters require additional power and produce waste heat, a scheme of fluid mixing with PID controlled valves is proposed, which can utilize thermal energies in different loop braches to control the temperature at the coldplate inlet by regulating valve openings. A numerical study is performed and its results show the system can satisfy the high precision temperature control requirement. The fuzzy PID control effect is better than that of the PID control algorithm, such as faster response, less overshoot, and higher control precision. Therefore, the fuzzy PID is preferred as the control algorithm of this scheme.

    References | Related Articles | Metrics
    A Cosmic Microscope to Probe the Universe from Present to Cosmic Dawn:Dual-element Low-frequency Space VLBI Observatory
    AN Tao, JAISWAL Sumit, MOHAN Prashanth, ZHAO Zhen, LAO Baoqiang
    2019, 39 (2):  242-249.  doi: 10.11728/cjss2019.02.242
    Abstract ( 791 )   PDF (776KB) ( 306 )   Save

    A space-based Very Long Baseline Interferometry (VLBI) program, named as the Cosmic Microscope, is proposed to involve dual VLBI telescopes in the space working together with giant ground-based telescopes (e.g., Square Kilometre Array, FAST, Arecibo) to image the low radio frequency Universe with the purpose of unraveling the compact structure of cosmic constituents including supermassive black holes and binaries, pulsars, astronomical masers and the underlying source, and exoplanets amongst others. The operational frequency bands are 30, 74, 330 and 1670 MHz, supporting broad science areas. The mission plans to launch two 30-m-diameter radio telescopes into 2 000 km×90 000 km elliptical orbits. The two telescopes can work in flexibly diverse modes. (i) Space-ground VLBI. The maximum space-ground baseline length is about 100 000 km; it provides a high-dynamic-range imaging capacity with unprecedented high resolutions at low frequencies (0.3 mas at 1.67 GHz and 20 mas at 30 MHz) enabling studies of exoplanets and supermassive black hole binaries (which emit nanoHz gravitational waves). (ii) Space-space single-baseline VLBI. This unique baseline enables the detection of flaring hydroxyl masers, and more precise position measurement of pulsars and radio transients at mas level. (iii) Single dish mode, where each telescope can be used to monitor transient bursts and rapidly trigger follow-up VLBI observations. The large space telescope will also contribute in measuring and constraining the total angular power spectrum from the Epoch of Reionization. In short, the Cosmic Microscope offers astronomers the opportunity to conduct novel, frontier science.

    References | Related Articles | Metrics
    System Design for the Event Horizon Imaging Experiment Using the PECMEO Concept
    2019, 39 (2):  250-266.  doi: 10.11728/cjss2019.02.250
    Abstract ( 1053 )   PDF (895KB) ( 2376 )   Save

    The concept for space interferometry from Polar or Equatorial Circular Medium Earth Orbits (the PECMEO concept) is a promising way to acquire the image of the “shadow” of the event horizon of Sagittarius A* with an angular resolution of circa 5 microarcseconds. The concept is intended to decrease the size of the main reflector of the instrument to about 3 m using a precise orbit reconstruction based on Global Navigation Satellite System (GNSS) navigation, inter-satellite range and range-rate measurements, and data from the Attitude and Orbit Determination System (AODS). The paper provides the current progress on the definition of the subsystems required for the concept on the basis of simulations, radio regulations, and available technology. The paper proposes the requirement for the localization of the phase centre of the main reflector. The paper provides information about the visibility of GNSS satellites and the needed accuracies of the AODS. The paper proposes the frequency plan for the instrument and its Inter-Satellite Links (ISLs). The concepts for measurement of range and range rate using ISLs (as well as for the data exchange at these ISLs) are presented. The block diagram of the interferometer is described and its sensitivity is estimated. The link budget for both ISLs is given as well as their critical components. The calculated measurement quality factors are given. The paper shows the expected performance of the sub-systems of the interferometer. The requirements for the localization of the main reflectors and the information about the availability of the GNSS satellites are based on the simulations results. The frequency plan is obtained according to the PECMEO concept and taking into account the radio regulations. The existing technology defines the accuracies of the AODS as well as the link budgets and the measurement accuracies for both ISLs and the sensitivity of the instrument. The paper provides input information for the development of the orbit reconstruction filter and the whole PECMEO system.

    References | Related Articles | Metrics