2017 Vol. 37, No. 1

Display Method:
Using Back Propagation Neural Network Method to Forecast Daily Indices of Solar Activity F10.7
XIAO Chao, CHENG Guosheng, ZHANG Hua, RONG Zhaojin, SHEN Chao, ZHANG Bo, HU Hui
2017, 37(1): 1-7. doi: 10.11728/cjss2017.01.001
The solar 10.7 cm radio flux,F10.7,a measure of the solar radio flux per unit frequency at a wavelength of 10.7 cm,is a key and serviceable index for monitoring solar activities.The accurate prediction of F10.7 is of significant importance for short-term or long-term space weather forecasting. In this study,we apply Back Propagation (BP) neural network technique to forecast the daily F10.7 based on the trial data set of F10.7 from 1980 to 2001.Results show that this technique is better than the other prediction techniques for short-term forecasting,such as Support Vector Regression method.
Two Upstream Splitting Schemes for Generalized Lagrange Multiplier Magnetohydrodynamics
ZHANG Jingke, LI Huichao
2017, 37(1): 8-18. doi: 10.11728/cjss2017.01.008
To develop a high performance MHD numerical simulation method is an important factor in research of numerical prediction of space weather. The upwind flux splitting scheme based on finite volume method has good ability to capture discontinuities. Steger-Warming and AUSM (Advection Upstream Splitting Method) schemes are two outstanding upwind flux splitting scheme, which are classified as FVS (Flux Vector Splitting) method. In this paper, these two schemes are applied to solve the Extended Generalized Lagrange Multiplier Magnetohydrodynamics (EGLM-MHD) equation with Galilean invariance. Results obtained from Orszag-Tang vortex and three-dimensional blastwave problem indicate that those two schemes are both robust and accurate. Particularly, AUSM scheme is superior to Steger-Warming scheme in divergence error control and computational speed.
IMF Sector Effect on Geomagnetic Field at MID and Low Latitudes during Solar Cycle 23
LI Zhongyi, LE Guiming, PEI Shixin
2017, 37(1): 19-27. doi: 10.11728/cjss2017.01.019
Geomagnetic data of Tianjing during solar cycle 23 have been analyzed by eigen vector method. The Interplanetary Magnetic Field (IMF) sector effect on the H component of geomagnetic field at mid and low latitudes has been studied. The results show that the sector effect magnitude is from 3 to 11nT at mid and low latitudes in contrast to tens nT at high latitudes. The IMF sector effect reached maximum (about 11nT) during solar activity maximum, and reached minimum (about 3nT) during solar activity minimum. The largest value of the sector effect during solar activity maximum occurred in spring, summer and autumn seasons. However, the largest sector effect occurred one year later in the winter season. In 1996 and 2007, when the IMF is away from (or toward) the Sun, the sector effect increase (or decrease) in H component at daytime and decrease (or increase) at night in summer, while the sector effect increase (or decrease) in H component at daytime during the other seasons. The sector effect causes opposite changes during solar maximum, however, it will have less effect during summer. For high solar activity years, the IMF sector effect on daily mean value variation of the geomagnetic field is the same (or opposite) with the decreasing (or increasing) phase of solar cycle. In the summer, the average increment minimum value arises, and the average increment is irregular. About 60% of the estimations are consistent with satellite observations in summer, spring and autumn months, but about 55% in winter months.
Solar Activity Dependence of Ionosphere Ion Upflow in the Polar Topside
FU Shuai, JIANG Yong, ZHAO Kai, JIANG Yi, SU Yucheng
2017, 37(1): 28-38. doi: 10.11728/cjss2017.01.028
The influence of solar activity on ionosphere ion upflow was studied, over the northern and southern hemispheric polar topside. The observations were obtained from the Defense Meteorological Satellite between 1995 and 2005. Results show that the response characteristics of upflow events on solar activity are roughly consistent for the two hemispheres, that is, ion upflow fluxes and ion densities are generally larger during high solar activity than those during low solar activity, but ion vertical velocities and upflow occurrence rates show an opposite variation trends, i.e., they are higher and more frequently seen under the conditions of low solar activity, respectively. Besides, we further calculated the mean value of upflow parameters in the southern hemisphere. The ratios of them under high and low solar activity conditions are about 2.26, 3.35, 0.71 and 0.51. Furthermore, the results also show that it is the ion densities instead of ion vertical velocities that have profound effect on the upflow fluxes. The causes of such a dependence is briefly analyzed. Under different levels of solar activity, ionosphere ion densities are different because of the variations of ionization rates and ion-neutral collision frequencies. The collision frequency between ion and neutral atmosphere is closely related to the ion density. Therefore, the ion upflow occurrence rate in the polar topside ionosphere depends on the level of solar activity.
Numerical Simulation of Ionospheric Disturbance Effects by Chemical H2O Release
GAO Ze, FANG Hanxian, WANG Sicheng
2017, 37(1): 39-49. doi: 10.11728/cjss2017.01.039
In order to study the perturbation effect of chemical substances in the ionosphere and its evolution on the later stage of development, based on a dynamical model including the neutral gas diffusion and chemical reaction, and a physical model developed to present the development of spread-F, through the release of H2O in the ionosphere, the distribution of electron, H2O, O+ and H2O+ are discussed and ionospheric disturbances by chemical release in point source, multiple source and line source are analyzed. Different release altitudes, different amounts of released substance and different release time are also compared. Besides, the developmental differences by different amounts of H2O are also simulated. The results show that:H2O can substantially decline electron density and facilitate the formation of ionospheric hole; the density distribution of O+ and H2O+ are elliptical; H2O released in different methods, such as, point source, multiple source and moving target line source, can cause different ionospheric disturbance effects, which confirm the possibility of artificially affecting a certain shape and area of the ionosphere; the disturbance amplitude of election density in lower altitude is larger than that in higher altitude and in daytime is larger than that in nighttime and the more H2O is released, the larger disturbance is caused; Chemical release in nighttime can trigger spread-F in ionosphere and the more is released, the better development is caused.
Study on Ionospheric Multi-mode Propagation Pollution Suppression Based on Time-frequency Analysis
LU Zhuanxia, LIU Wen, LI Xue, LI Jining, GUO Wenling
2017, 37(1): 50-58. doi: 10.11728/cjss2017.01.050
The high resolution linear time-frequency analysis method and the combined time-frequency analysis method are the theoretically analyzed and verified by simulation in this paper. And these two methods are applied to high frequency ionospheric backscattering detection data that have ionospheric multi-mode propagation state. The effect of ionospheric pollution suppression is analyzed. Results show that these two methods have better effect in the case of ionospheric multi-mode propagation state and phase pollution exist at the same time. These two methods can make spectrum more sharpening than other conventional methods. The ship target is clearly revealed in time-frequency domain. Thus it is proved that these two methods have very high application value. For sky-wave over-the-horizon radar detection of low speed targets like ships, these two methods are of great significance.
Effects of Pre-heating Time on Pre-heating Amplitude-modulation in the Lower Ionosphere
YANG Ding, FANG Hanxian, MA Qiang, WANG Sicheng
2017, 37(1): 59-66. doi: 10.11728/cjss2017.01.059
Based on the energy conservation equation and electron continuity equation, the pre-heating amplitude-modulated theoretical model for the lower ionosphere is established. Then, the oscillations process of ionospheric conductivity and current, which amplitude are modulated by high power electric wave are simulated. Furthermore, the effects of pre-heating time on Extremely Low Frequency/Very Low Frequency (ELF/VLF) radiation levels are studied thoroughly. The results indicate that the electric current in the lower ionosphere can be modulated effectively by high power electric wave, and can be used as the radiation source of ELF/VLF. The longer the pre-heating time is, the more effectively the pre-heating amplitude-modulated model is. If taking the energy loss into account, as the heating conditions are PER=200MW and fELF/VLF=1kHz, the effect of ELF/VLF radiation with the pre-heating amplitude-modulated model is the best when the pre-heating time is 0.1s. And the ELF/VLF radiation levels are improved by 7.95dB.
Real-time Monitoring Regional Ionospheric Variety of China with BDS Observations
DONG Enqiang, CAO Yueling, GONG Lei, LIU Xiaoping, CHANG Zhiqiao, WU Xiaoli
2017, 37(1): 67-74. doi: 10.11728/cjss2017.01.067
BDS provides uninterrupted PNT service for Asia-Pacific area since 27 December 2012, when China released an official version of the complete BDS Interface Control Document (ICD) for open service Signal-In-Space (SIS). Because BDS signals working at three frequencies, ionospheric delay can be calculated with pseudo-range dual-frequency combination technique and a new technique to monitor ionospheric variety over China is established. Lower-middle latitude area of China is in the ionospheric equator anomalies region and large grads ionospheric varieties often occur within the area of north latitude 20°±5°. Daily variety characteristic of ionospheric delay measured with BDS GEO satellites is analyzed by using BDS real-time pseudo-range observation and adopting carrier phase smoothed pseudo-range. China region ionospheric map is painted in 1°×1° scale with polyhedral fitting every 5 minutes and the average fitting error RMS of all Ionospheric Punch Point (IPPs) is 2.778TECU. The ionospheric anomalies around China monitored with BDS observation shows that the VTEC peak difference between adjacent two days can be 60TECU when large scale ionospheric anomaly occurs.
Measurements of Lower Mesosphere Inversion Layers with Rayleigh Lidar over Beijing
CHEN Linxiang, YANG Guotao, WANG Jihong, CHENG Xuewu, YUE Chuan
2017, 37(1): 75-81. doi: 10.11728/cjss2017.01.075
By using the measurement data of Rayleigh Lidar located in Yanqing, Beijing (40.47°N, 115.97°E) during the period from January to February 2012 and from May 2012 to April 2013, statistic characteristics of lower Mesosphere Inversion Layers (MIL) occurring between 60 and 80km altitude over North China have been reported. The occurrence of lower MIL in Beijing was found to be 65% in this period. The mean bottom/top height was 68.2km (73.0km) and mean thickness was 4.8km. 47 inversion events propagated downward while 12 inversion events propagated upward in 91 lower MIL events. Notably, 3 double lower MIL events vertically propagated in quite different speed and direction. During the double lower MIL on 17 May 2012, the upper MIL and the lower MIL propagated downward with vertical speed of 610m·h-1 and 460m·h-1 respectively. And during the double lower MIL observed on 8 February 2013, the upper spread propagated upward while the lower spread propagated downward with vertical speed of 512m·h-1 and 263m·h-1 respectively. However, during the double lower-MIL on 18 February 2013, the lower MIL was spreading downward with a speed of 1300m·h-1 with inversion amplitude increasing. After the amplitude reached its maximum value, a weak shallow upper-MIL was split out from the MIL. All these are analyzed in detail.
Statistical Characteristics of Albedo Variation in Noctilucent Clouds Induced by Small-scale Gravity Waves
GAO Haiyang, ZHANG Zuyi, BU Lingbing, HUO Chaoyang, WANG Zhen, ZHU Hong
2017, 37(1): 82-93. doi: 10.11728/cjss2017.01.082
The accurate assessment of albedo variations in Noctilucent Clouds (NLC) induced by Gravity Waves (GW) has shown an important significance in evaluating the trend of NLC brightness. This work focuses on the impact of small-scale GW with wavelength of 10~150km on the albedo of Polar Mesospheric Cloud (PMC). Using the Level2 albedo images obtained by the Cloud Imaging and Particle Size (CIPS) experiment onboard Aeronomy of Ice in the Mesosphere mission (AIM) from 2008 to 2009, 6664 small-scale GW are extracted. The wavelength of those GW is from 10 to 150 kilometers. By comparing and analyzing the albedo in GW areas and in mean NLC areas, the characteristics of the albedo variations in NLC induced by small-scale GW are studied. Results show that the albedo variations are primarily positive, and the maximum average value, 4.48×10-6sr-1, is found on the descending portion of South Hemisphere. The albedo and Ice and Water Contents (IWC) variations are positively correlated, and the correlation coefficients are greater than 0.85. The albedo variations largely rely on the location and time of the GW, and the mean albedo variations are almost positive. The albedo variations are larger in higher latitude during the core of the seasons, while they become smaller gradually in lower latitude during the beginning and ending period of the seasons, and even to be negative in some edges of the maps. The albedo average value increases linearly as the background atmosphere increases, and the albedo variations in percentage is from 14.6% to 28.8% induced by small-scale GW. When the albedo amplitude of GW increases, the albedo variations also show a linear increase with the changing rate from 0.909 to 1.194. The whole variation rate of south hemisphere is a little smaller than that of north hemisphere because of the difference of background atmospheric conditions.
A Data Preprocessing Method and Preliminary Results of All-sky Airglow Image
DUAN Boqiang, PAN Weilin
2017, 37(1): 94-104. doi: 10.11728/cjss2017.01.094
Abstract(1116) PDF 4881KB(1465)
Atmospheric Gravity Wave (AGW) is one of the fundamental waves in the atmosphere, which plays a significant role in the dynamics and thermal balance of the Mesosphere and Lower Thermosphere (MLT) region. By tracing the atmospheric airglow radiation, all-sky airglow imager can effectively image atmospheric gravity waves. In this paper, an image processing method for the data of OH airglow imager at Xining Station (36.6°N, 101.7°E) is presented. The imager was independently designed by State Key Laboratory of Space Weather of the CAS National Space Science Center. A typical gravity wave-event was observed using this imager on 17 May 2015. Finally, the OH airglow data obtained by observation experiments in Xining (on 17 May 2015 at 21:00BLT to 05:00BLT on the next day) is analyzed by this method. The horizontal wavelength, phase velocity and propagation direction of the gravity wave are successfully extracted, which proved the method is feasible and robust.
Optimal Impulsive Design for Aeroassisted Orbit Transfer in Noncoplanar Orbit Debris Remove
YAN Ruidong, WANG Ronglan, LIU Siqing, SHI Liqin, GONG Jiancun
2017, 37(1): 105-113. doi: 10.11728/cjss2017.01.105
Noncoplanar orbit transfer of debris remove vehicle needs lots of fuel. In this paper the optimal impulsive design for aeroassisted orbital transfer from Low Earth Orbit (LEO) or Geostationary Earth Orbit (GEO) to LEO with an inclination change is presented. Through comparison of the double-impulsive Hohmann orbit transfer and aeroassisted orbit transfer in noncoplanar orbit, the fuel savings of different altitude or inclination from two noncoplanar orbits are concluded. Results show that the minimum velocity increment of orbit transfer between GEO and LEO is 1.55km·s-1. With the increase of orbital altitude difference, aeroassisted orbital transfer efficiency gradually reduces. Implementation of aeroassisted orbit transfer with the same orbital altitude, low orbit aeroassisted orbit transfer optimization efficiency is higher than that of high orbit. When the value of orbital inclination between two noncoplanar orbits is less than 5°, the fuel consumptions by adopting aeroassisted orbit transfer and double impulse orbit transfer are equal. For aeroassisted orbit transfer optimization between noncoplanar orbits with the same altitude but different orbital inclination difference, with the increase of orbit inclination difference, the fuel saving first increases then decreases, and when the angle is about 20°, the fuel savings rate is the maximum.
Thermal Design and Validation of DAMPE BGO Calorimeter
HU Yiming, CHANG Jin, CHEN Dengyi, LIU Shubin, FENG Changqing, ZHANG Yunlong
2017, 37(1): 114-121. doi: 10.11728/cjss2017.01.114
Abstract(1217) PDF 6197KB(1524)
Dark Matter Particle Explorer (DAMPE) is one of the first scientific exploration satellites of China, aiming to search dark matter by measuring the spectrum of electron/positron and gamma ray. DAMPE mainly consists of four sub-detectors including Plastic Scintillator Detector (PSD), Silicon Tungsten Tracker (STK), BGO Calorimeter (BGO) and Neutron Detector (NUD). As the most important sub-detector of DAMPE, BGO calorimeter plays a key role in precisely measuring energy of the incident cosmic ray and identifying particles. In this paper, thermal design of the calorimeter is introduced. Based on this design, the Finite Element Analysis (FEA) on temperature field of the BGO calorimeter is performed with the given on-orbit conditions. In the end, Thermal Vacuum (TV) test has been carried out in March, 2015 to prove the FEA is correct and the methodology in this paper is effective.
Magneto-elastic Buckling Analysis of Electrodynamic Space Tethers
GUO Caifa, CHEN Hongying, YUAN Xiaojiang
2017, 37(1): 122-128. doi: 10.11728/cjss2017.01.122
The magneto-elastic buckling problem is a hot topic of Electrodynamic Tether (EDT) system because of its strongly nonlinear dynamics and the existence of complicated multi-fields coupling problems. An elastic rod model for EDT is established based on the geometrically exact Kirchhoff equations, and the effect of geomagnetic environment on EDT is analyzed. The static and dynamic instability of EDT are thoroughly studied, and the critical value of magnetic field as the bifurcation happens is calculated. The results show that the critical value decreases as the angular velocity increases, which can provide a reference for the current and other parameters design of EDT.