Subjects: Geosciences >> Space Physics submitted time 2016-05-04
Abstract： OH airglow emissions are generated in the mesopause and low thermosphere (MLT) region in a layer centered near 87km.The OH rotational temperature is a good proxy for the kinetic temperature.So the rotational temperatures derived from ground-based observations of OH airglow emissions are used to investigate the temperature structure in the MLT.The OH airglow emission spectra were observed by the ground-based spectrometer from December 2011 to December 2013.The OH (8-3) band is used to calculate rotational temperature.The temperatures from SABER are weighted vertically by the weighting functions from its OH-A channel volume emission rates.Firstly, the rotational temperature is compared with the SABER.Secondly, the daily mean temperatures are fitted by the harmonic waves, and the temporal variation features during nights are analyzed.The comparison between OH rotational temperature and SABER shows that the mean rotational temperature of OH (8-3) band is 203.011.2Kwith 5.5Kwarmer than SABER′s.Both have obviously identical seasonal variations and the temperature variation of winter to summer can reach 60K.The annual and semiannual components are the two most significant variations, and the annual amplitude of 10.8Kis greater than semiannual amplitude of 2.7K.Their phases are respectively in December and March.It is shown that there are multiple temporal rotational variations during night, such as oscillations controlled by tides and shortperiod waves.The OH rotational temperature is a good proxy for the kinetic temperature in the MLT region.There are significant annual and semiannual variations in this region, and the temperatures during night have various temporal features.It is concluded that the temporal variations of ground-based rotational temperatures from OH (8-3) band are well correlated with the SABER temperatures.They have the same seasonal variations and the annual and semiannual oscillations are the two strongest components.The nocturnal rotational temperatures have multiple temporal features controlled by the various oscillations.
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Awaiting Review
Subjects: Geosciences >> Space Physics submitted time 2016-05-04
Abstract： Large planar plasma sheets with size of 60 cm*60 cm, maximum current of 3 A and duration of 200 mus, were obtained in a pulsed linear hollow cathode discharge device under 15 mT magnetic field confinement. The electron density 2-D distribution in the thickness direction and its evolution of plasma sheets with pressures between 90 Pa to 210 Pa were obtained by Langmuir probe using the fast frame function of oscilloscope and the rotating hollow cathode method. The effects of pressure on the time needed to reach the maximum peak density in the thickness direction, the maximum peak density and the full width at half maximum (FWHM) peak density, were investigated. The results show that, as the pressure decreased, the time reaching the maximum peak density in the thickness direction and the FWHM peak density diminished, while the maximum peak density in the thickness direction increased. These results could be utilized to manipulate the parameters of large planar plasma sheets.
Peer Review Status:Awaiting Review
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： In order to choose the best detection efficiency of different formations, quantitative evaluation of different formations shall be employed. In this paper, the existing evaluation parameters of four-point cooperative detection are analyzed and summarized and then based on the definition of volumetric tensor, the five-point formation is divided into five tetrahedrons and one main tetrahedron plus a fifth point to evaluate the detection efficiency. Finally, orbit data of five-spacecraft in one orbit period is used to simulate and analyze the two methods, and result shows that the method works well in evaluating five-point formation.
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 Subjects: Geosciences >> Marine Sciences submitted time 2016-05-03
Abstract： In order to study the feasibility of ocean surface current measurement using radar scatterometer, the system parameters of the traditional scatterometer were modified, the coherent coefficient model and decorrelation factors were derived, and the phase error model was obtained. Moreover, this paper established an end-to-end model to simulate the ocean surface current measurement. The input wind speeds ranged from 2m/s to 21m/s and the wind direction was parallel to the cross track direction. The results show that the current speed standard deviation in along-track and cross-track direction are smaller than 0.1m/s, when the wind speed is greater than 5m/s. And the swath that can be used for current speed inversion is greater than 40%, when the wind speed is larger than 7m/s. The width of effective swath increases with the increase of the wind speeds. After parameters' optimization, communication error was calculated and the results show that the communication error of the modified scatterometer is better than that of the fan-beam, rotating scatterometer in both the low wind speed and high wind speed conditons. � 2015, Chinese Institute of Electronics. All right reserved.
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： Millimeter-wave space-borne antennas with multi-band and multi-polarization have many advances such as high gain,low side-lobe,high beam efficiency and low loss.The operating frequency of the antenna includes 18.7,23.8 and 37.0 GHz.The use of common feed system has significance for saving volume and enhancing structure stiffness.And the ring-loaded corrugated conical horn can cover octave bandwidth.The orthomode transducer(OMT)with new turnstile junction and frequency divider was employed to separate dual polarizations signals and then divide different frequencies into their own receivers,respectively.The cross polarization levels are -32.6,-31.6 and -25.0 dB in 18.7,23.8 and 37.0 GHz,respectively.The side lobe levels are -21,-30 and -30 dB.Due to compact structure and multiple observations for one target,the simulation result demonstrates the design of feed system is suitable to space-borne antennas.
Peer Review Status:Awaiting Review
Subjects: Geosciences >> Space Physics submitted time 2016-05-03
Abstract： To realize remote sensing at sub-millimeter wavelengths,a 450 GHz sub-harmonic mixer was studied. An anti-parallel pair of Schottky diodes is the key component in the mixer. The length of the diodes is 74 mum,and the cutoff frequency of diodes is up to 8 THz. The suspended microstrip matching circuit was built on quartz,and the metal block was cut into two halves. The diode embedding impedance was calculated. The diode package and the matching circuit were integrated in the mixer model. The predicted single side band (SSB) conversion loss is 8. 0 dB,with 4 mW of local oscillator power. Measured results indicate that the lowest measured SSB conversion loss is 14. 0 dB, with 5 mW of local oscillator power. The loss is below 17. 0 dB in the band from 433 ~ 451 GHz,with a 3 dB bandwidth of 18 GHz.
Peer Review Status:Awaiting Review
Subjects: Geosciences >> Space Physics submitted time 2016-05-03
Abstract： According to the level of domestic processing technology at present,the circuit structure of anti-parallel diodes with self-bias was proposed. With this structure, not only the difficult problem of processing bias circuit can be solved, but also the odd-order frequency multiplication can be realized efficiently. At the meantime, co-simulation approach was used to simulate the electrical characteristic of the tripler by software HFSS and ADS,including the impact of the parastics. After designing, both the machining and electrical installation are accomplished. The highest measured output power is 3.1 mW at 221 GHz and the output power is more than 2 mW at frequencies of the range 219~227 GHz. These results can provide important reference for future design of high efficiency submillimeter frequency multiplier.
Peer Review Status:Awaiting Review
Subjects: Geosciences >> Space Physics submitted time 2016-05-03
Abstract： A novel single layer microstrip reflectarray element with multi-resonance structure is proposed in this paper.HFSS soft ware is used to analyze the reflect phase for the designed element.About 430皉eflect phase range is obtained with the reflect phase curve nearly linear.A microstrip reflectarray composed of the proposed element is designed for Ku band and a Vivaldi antenna is used as the feed.The results indicate that the gain reaches 27.1 dB at the center frequency,and the half power beamwidth is 4.96�The gain changes less than 2 dB in the range of 12~15.5GHz,which shows that the reflectarray has wide band.The Vivaldi antenna and the reflectarray is manufactured and tested,and a well coincide is obtained between the simulation results and the test results.
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： After spacecraft launched into space environment, molecule contamination and tiny particle contamination deposit on spacecraft surface and constitute the surface contamination layer. This contamination phenomenon has different levels of negative impacts on some technical systems. The on-orbit detection results of spacecraft surface contamination both in China and abroad were discussed. Surface contamination deposition changes and control factors were preliminarily evaluated. The result shows that deposition changes of surface contamination within the first 1 to 2 years after launch are controlled by the spacecraft outgassing mass by itself, outgassing rate, spacecraft surface temperature and air flow direction. The deposition mass within early period is larger, which is controlled by more surface outgassing by spacecraft itself within early period and higher deposition rate after launch. And the deposition mass is more in the ram area than in the yield area. The surface deposition in the later period shows obvious drop or slow fluctuations, and possesses omnidirectional characteristics. Some control factors with omnidirectional effect were discussed, among which high-energy particle flux and solar ultraviolet radiation flux may be the main control factors.
Peer Review Status:Awaiting Review
Subjects: Geosciences >> Space Physics submitted time 2016-05-03
Abstract： Gravity wave activity in the upper stratosphere is investigated using density data retrieved from the Rayleigh lidar of National Space Science Center, Chinese Academy of Sciences. Combining the Rayleigh lidar data with the wind data of National Centers for Environmental Prediction (NCEP) Global Forecast System (GFS), we study a mountain wave observed on November 11, 2013. The parameters of this mountain wave, such as propagation direction and propagation speed, have been calculated. Gravity wave perturbations are extracted from 0.5 h×1 km density profiles. The relative density perturbations are expressed by ρ'(z)=(ρ(z)-ρ0(z))/ρ0(z), where ρ(z) is the measured atmosphere density, and ρ0(z) is the background density which is calculated by fitting the logarithmic form of whole night mean density with 4 order polynomial. The background wind data are achieved by applying a linear polynomial fitting to the NCEP-GFS wind data between 20 to 48 km altitude. Using the data extracted from the complete density perturbations structure and the background wind data, we calculate the parameters of gravity waves observed on November 11, 2013 by the gravity wave dispersion equation. The complete density perturbation structure shows an obvious phenomenon of mountain gravity wave activity. The wave phases at same altitude remain unchanged in the whole night. The perturbation structure shows that vertical wavelength is about 5.5 km but changes with altitude. A group of over-determined equations can be established by substituting the data extracted from the complete density perturbations structure and the background wind data into the gravity wave dispersion equation. And two groups of solutions are obtained by using the least squares method to solve these over-determined equations. The wind profiles in the direction of two sets of solutions have been analyzed. A critical layer (zero wind layer) which will prevent the upward propagation of mounting waves is found in the wind profile in the direction of 37.9°(or 217.9°). Finally, the gravity waves observed on November 11, 2013 propagate in the direction of 52.4° from the north to the west, with a horizontal wavelength of 5.5 km. Compared with inertia waves, there is no downward-propagating or upward-propagating phase in the density perturbation structure. At the same altitude, the phase remains unchanged in the whole night. Such kind of gravity wave perturbation structures have been often observed in winter. Density data obtained by Rayleigh lidar and NCEP-GFS wind data at Beijing are used to analyze a mountain wave parameters observed on November 11, 2013. By analysis, we obtain terrain-generated gravity waves propagating in the direction of 52.4° from the north to the west, with a horizontal wavelength of 5.5 km and average vertical wavelength of 6.0 km. ©, 2015, Science Press. All right reserved.
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
Subjects: Geosciences >> Space Physics submitted time 2016-05-03
Abstract： The classical approaches for single event latchup (SEL) rate prediction are based on the rectangular parallelepiped (RPP) model of only one sensitive volume. However, the experiment results of SEL sensitivity mapping of static random access memory (SRAM) show that the device has not only one sensitive volume (SV). The in-flight SEL rate of the device was corrected using the experiment results of pulsed laser SEL sensitivity mapping of SRAM K6R4016V1D.The SEL sensitivity maps of the SRAM by pulsed laser were first obtained and then the SV number of the device was calculated. The SEL rates of the device were predicted and discussed for different space orbits, radiation particles, SV thicknesses and SV number in particular. The results show that SEL rate caused by heavy ion decreases with SV number. The correction of the SV number is essential for SEL rate due to proton direct ionization; otherwise, the contribution of direct ionization of protons to SEL rate would be greatly overestimated.
Peer Review Status:Awaiting Review
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