Subjects: Geosciences >> Space Physics submitted time 2016-05-04
Abstract： Large planar plasma sheets, generated by a linear hollow cathode in pulse discharge mode under magnetic confinement, can be used in the field of plasma antenna, plasma stealth, and simulation of a plasma layer surrounding vehicles traveling at hypersonic velocities within the Earth's atmosphere. Firstly, to investigate the propagation properties of electromagnetic waves at different frequencies and polarization, the transverse field transfer matrix method is introduced. Secondly, the measured electron density temporal and spatial distribution and the transverse field transfer matrix method are utilized to calculate the reflection, transmission and absorption of electromagnetic waves by large planar plasma sheets with different currents. Finally, 1 GHz (less than the critical cut-off frequency) electromagnetic waves and 4 GHz (greater than the critical frequency) electromagnetic waves are chosen to investigate the evolution of propagation properties during the pulsed discharge period. Results show that both the reflection and absorption of the electromagnetic waves are greater for their polarization direction parallel to that of magnetic field, and their frequencies lower than the critical cut-off frequency, and as the discharge currents rise, the reflection increases while the absorption decreases. However both the reflection and absorption of the electromagnetic waves with their polarization direction perpendicular to the magnetic field direction and their frequency greater than the critical cut-off frequency become less, and as the discharge currents rise, both the reflection and absorption will increase. For the electromagnetic waves with their polarization direction perpendicular to the magnetic field direction, there is an upper hybrid resonance absorption band near the upper hybrid resonance frequencies, in which the absorption is significant but the absorption peak value is not affected by the discharge current. The propagation characteristics of the electromagnetic waves with polarization direction perpendicular to the magnetic field direction are the same as that of the electromagnetic waves with the polarization direction parallel to the magnetic field direction, except the upper hybrid resonance absorption. During the pulse discharge period, the propagation characteristic of the electromagnetic waves experiences an unstable phase before reaching steady states. The transition time is about 100 mu s and increases as the discharge current rises. The upper hybrid resonance absorption is significant during the phase of steady state for waves with frequency lower than the critical cut-off frequency and polarization direction parallel to the magnetic field direction. For the applications of a large planar plasma sheet to reflect electromagnetic waves effectively and steadily, the pulse discharge period should be larger than 100 mu s, and its discharge current should be large enough to make the critical cut-off frequency greater than the frequency of incident wave, and its polarization direction should be parallel to the magnetic field direction.
Peer Review Status:
Awaiting Review
Subjects: Geosciences >> Space Physics submitted time 2016-05-04
Abstract： The study of the ionosphere responses to Corotating Interaction Regions (CIRs) and Coronal Mass Ejections (CMEs) got much attentions in rencent years. With the comparison of different types of ionosphere response caused by different disturbance sources from solar activity and interplanetary solar wind, morphological changes and physical process of ionospheric storms can be understood more impressively and comprehensively. It provides a possibility to predict ionospheric disturbance states according to different solar wind conditions in advance as well. GPS-TEC data at a mid-latitude station (131 degrees E, 35 degrees N) are used to analyze the ionosphere response during geomagnetic disturbances induced by 109 CIRs and 45 CMEs over the period 2001 to 2009. Firstly, the TEC difference are determined to achieve the information of ionospheric positive or negative storms during the CIR and CME events. The definition of a ionospheric storms is relative TEC greater than or equal to 15% and persisting for more than 4 hours; Secondly, year dependence, seasonal dependence, time delay between ionospheric storms and geomagnetic storms, geomantic storm intensity dependence and time duration of ionospheric storms are analyzed in detail. Analysis results indicate that the types of ionospheric storms vary in different phases of a solar cycle. CIR-driven positive and positive-negative storms are more likely to occur in the declining phase of the solar cycle, while negative phase storms more in solar maximum and negative-positive storms mainly in solar minimum. CME-driven positive storms and negative storms mostly occur in solar maximum. There is no remarkable seasonal difference for the occurrence of different types of ionospheric storms except the positive-negative storms most likely to occur in summer. The time delays between geomagnetic disturbances and the start time of ionospheric storms are-6 to 6 hours in general, but CIR-driven ionopsheric storms involve in a wider range with a time delay of-12 to 24 hours and CME-driven storms is delayed from 6 to 6 hours. Moreover, for CIR-driven ionospheric storms, positive and negative storms mostly occur in main phase of magnetic storms, positive-negative storms mostly in initial and main phase, and negative-positive storms mainly in initial phase. For CME-driven storms, positive, negative and positive-negative storms basically occur in main phase. Our investigation also demonstrates certain correlation between the types of ionospheric storms and the AE maximum indices. Ionopsheric negative storms often occur in stronger geomagnetic activity, with the AE maximum intensity between 800 to 1200nT while positive-negative storms tend to occur with AE maximum intensity higher than 400 nT. Compared to CIR driven storms, AE maximum value during CME driven storms is higher. The duration of CIR-driven storms is longer (1 to 6 days) than that of CME-driven storms (1 to 4 days). The ionosphere response to interplanetary conditions contribute to the study the ionospheric disturbance. Statistical analysis of the ionosphere response to the CIR and CME in Mid-latitude regions indicate that there are some certain correlations among ionospheric changes, solar activities, interplanetary conditions and geomagnetic conditions. The ionospheric storms could be predicted more accurately and meticulously by distinguishing the different types of interplanetary conditions.
Peer Review Status:Awaiting Review
Subjects: Geosciences >> Space Physics submitted time 2016-05-04
Abstract： Aiming at requirement of high speed and complete of data in space storage system, the design of a high performance NAND Flash controller is present. It concludes a pipelining-programming inside of NAND Flash chip and a non-missing invalid block method. The storage implementation is present. The calculation of storage time in different situation is discussed. The simulation modules are present and the impact of pipelining programming is simulated and discussed using Monte Carlo method. Practical application proves the pipelining programming and non-missing invalid block method. The operation frequency of storage system achieves to 100MB/s, ensuring accuracy, completeness and continuity of data.
Peer Review Status:Awaiting Review
Subjects: Geosciences >> Space Physics submitted time 2016-05-04
Abstract： For deep space communication paths close to the sun causing solar scintillation of radio waves and increasing bit error rate(BER),the approach of choosing the signal bandwidth in the non-frequency selective and slow fading channel with maximum time was proposed.The deep space communication channel model was built based on Rician fading channel model.The statistical characteristics of the amplitude, the coherence time and the coherence bandwidth of the channel were used.The difference among solar scintillation,mobile multipath and ionosphere scintillation was compared. Based on the change of the coherence time and coherence bandwidth with solar elongation angle,the time-selective and frequency-selective characters were determined. Simulation results show that at different little solar elongation angle,especially the small one,the BER of the signal bandwidth chosen by the proposed approach is better than the BER of other signal bandwidth.
Peer Review Status:Awaiting Review
Subjects: Geosciences >> Space Physics submitted time 2016-05-03
Abstract： The Range Migration Correction (RMC) is a key technique of synthetic aperture radar altimeter which is more precise than the conventional radar altimeter. Because of the satellite motion, the distance change between the satellite and the observed target will bring about some residual errors, but they are ignored in the existing RMC algorithms. In this paper, the influences of the vertical and horizontal velocities of the satellite are studied, then an RMC model is builded, and finally a new RMC algorithm which corrects not only the slant range error but also the residual errors is proposed. The simulation results show that this new algorithm can obtain more accurate outcomes. �2015, Science Press. All right reserved.
Peer Review Status:Awaiting Review
Subjects: Geosciences >> Space Physics submitted time 2016-05-03
Abstract： A mould method used in polarized wire grid fabrication is proposed.The grids with analytical and computer simulation analysis method is designed.A variety of specifications,different aperture and grid frame materials for microwave/millimeter wave band used the mould method is produced.This series of polarized wire grid is tested by the liquid nitrogen environment,mechanical and electrical performance test.The results show that the polarized wire grid has strong environment adaptability,high mechanical precision and excellent electrical performance,and can meet the demand of practical application,which develop a new method for millimeter wave polarized wire grids localization.
Peer Review Status:Awaiting Review
Subjects: Geosciences >> Space Physics submitted time 2016-05-03
Abstract： The radio occultation (RO) technique using signals from the global navigation satellite system, is widely used to observe the atmosphere for applications such as numerical weather prediction (NWP) and global climate monitoring. Since 1995, there have been turborogue sounder on board global positioning system/meteorology, black jack sounder on board challenging minisatellite payload and gravity recovery and climate experiment, IGOR sounder on board constellation observing system for meteorology, ionosphere and climate, GRAS on board meteorological operational, which have been recieving a large number of RO data, but their observed signals come only from global positioning system (GPS). These RO data have been wildly used in NWP and climate monitoring, however they cannot meet the requirements for high accuracy and real time atmosphere observation, in this case compatible RO sounder to obtain more RO observations is significant. Global navigation satellite system occultation sounder (GNOS) on board the fengyun3 C (FY3 C) satellite, which is the first Bei Dou system (BDS)/GPS compatible RO sounder in the world, was launched on 23 September 2013. Up to now, lots of RO observations have been obtained. In this study, the components of GNOS are introduced; one-day GNOS RO events and their global distribution are analyzed; compared with the GPS RO observations, the accuracy and consistency of BDS real-time positioning results and BDS RO products are analyzed. The preliminary results show that the BDS can enhance the number of RO events by 33.3%; the average deviation and standard deviation of BDS real time positioning results are 6 m and 7 m, respectively; the BDS/GPS difference standard deviation of refrectivity, temperature, humidity, pressure and ionospheric electron density are lower than 2%, 2 K, 1.5 g/kg, 2%, and 15.6%, respectively. The BDS observations/products are consistent with those of GPS, therefore BDS RO products can bring benefit to numerical wheather prediction and global chlimate change analysis.
Peer Review Status:Awaiting Review
Subjects: Geosciences >> Space Physics submitted time 2016-05-03
Abstract： Drag coefficient sequence C_d is obtained by solving Tiangong 1 continuous 55 days (d)GPS orbit data with different arc length. The same period solar radiation flux f_(10.7)and geomagnetic index a_p,A_p sequences are high and low frequency multi-wavelet decomposed. Statistical analysis results of the multilayer sliding correlation between space environmental parameters and decomposition of C_d show that lag correlation between the satellite drag coefficient sequence after wavelet decomposition and the corresponding level of f_(10.7),A_p sequence is good. It is also verified that the C_d prediction is feasible. Prediction residuals of Cd with different regression models and different sample lengths are analyzed. The results show that the case setting sample length of 20 days and selecting f_(10.7)regression model is best. It is also show that NRLMSIS-00 model's response in the region of 350 km (Tiangong's altitude)and low-middle latitude (Tiangong's inclination)is excessive during the ascent phase of geomagnetic activity A_p and is inadequate during decline phase. Additionally,for the low-frequency decomposition sequence NRLMSIS-00 model's response is appropriate during the ascent rising phase of f_(10.7). For the high frequency decomposition sequence,NRLMSIS-00 model 's response is small-scale inadequate during the ascent phase of f_(10.7)and is excessive during the decline phase of f_(10.7). Finally,the summary of potential use and outlook are listed; this method has an important reference value for improving the spacecraft orbit prediction accuracy.
Peer Review Status:Awaiting Review
Subjects: Geosciences >> Space Physics submitted time 2016-05-03
Abstract： The pulsed laser facility for single event upset(SEU)sensitivity mapping was utilized to study SEU sensitivity mapping of SRAM IDT71256.To avoid the block of the metal layer in the front side of integrated circuit,the backside testing method was used.The experiment results show that the SEU sensitivity of the SRAM cell depends on the pattern of data stored in the memory cell.The SEU sensitivity mapping could be used to construct the corresponding SEU cross section,which is validated by the heavy ion beam test result.
Peer Review Status:Awaiting Review
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