Subjects: Geosciences >> Space Physics submitted time 2017-01-22
Abstract： Based on an extremely disturbed field-aligned electrons event observed with Cluster in the northern cusp region on September 30, 2001, the energy features of the field-aligned electrons in the event was analyzed and the role of the field-aligned electrons on the solar wind energy transfer into the magnetosphere and on the magnetosphere-ionosphere coupling. The results show that the velocities and densities of the electrons have strong disturbances during the event, and the velocity is main factor to enhance the electron flux. The energy spectrum in the 5~200eV and 500~1500eV show that the up-flowing electron flux is higher than down-flowing, which means the up-flowing electrons are from the ionosphere and play a active role in this event. The features of the energy show that the ionospheric electrons have been accelerated during the up-flow. However, the physical mechanism still needs to be further studied.
Peer Review Status:
Awaiting Review
Subjects: Geosciences >> Space Physics submitted time 2016-05-13
Abstract： The spaceborne sodium Doppler lidar can be developed to measure global wind, temperature and sodium number density in the mesopause and lower thermosphere region. In order to analyze the feasibility of the lidar, simulation calculations about backscattering signals and measurement accuracy have been done in this paper. The analyzed result shows that the line-of-sight wind accuracy, horizontal wind accuracy and temperature accuracy are 0.8 m/s, 1.5 m/s and 2.5 K when the height of satellite orbit is 400 km, observational angle is 30.0� laser power is 9.0 W, receiver diameter is 1.0 m, vertical range resolution is 2.0 km, and signal integrated time is 30.0 s.
Peer Review Status:Awaiting Review
Subjects: Geosciences >> Space Physics submitted time 2016-05-13
Abstract： According to the databases of AP-8 and CRRESPRO proton radiation belt models, comparison between both models on the magnetic equator is carried out and reasons for their differences are presented. The model of proton radiation belt for the peak radiation region is developed by using the analytic function, which includes the submodel for relationship between the L value corresponding to the peak value of omni-directional proton differential flux (L_c) and the proton energy, and the submodel for relationship between the peak value of omni-directional proton differential flux J_(max) and the proton energy. Finally, the observation of energetic proton on the magnetic equator from RBSP A satellite's REPT telescope is used to compare with the results from AP-8 model,CRRESPRO model and the central radiation model. It is found that the values of omni-directional proton differential flux for 78.9, 102.6 and 208 MeV channels from RBSP A satellite are obviously larger than those from the three models, but the values of L_c from RBSP A satellite are very close to those from AP-8 model and the central radiation model, and RBSP satellite also observes the hidden secondary proton radiation belt presented by CRRESPRO Quiet model.
Peer Review Status:Awaiting Review
Subjects: Geosciences >> Space Physics submitted time 2016-05-13
Abstract： The facility for combustion experiments in space is lightweight, small sized and multi- functional. In this paper, a prototype system used for flame structure display and temperature measurement is presented, which combined the schlieren method, rainbow schlieren deflection method and differential interference method. It is also lightweight and small sized. As for the prototype system, the flame structure display function was checked by schlieren method in microgravity drop tower, and the temperature measurement function was checked by rainbow schlieren deflection and differential interference method under normal gravity condition. Results show that the resolution of flame structure was not less than 1 mm, and temperature field measurement was accurate with relative error smaller than 2%. Such prototype system is important to the promotion of space combustion science experiment technology and will be beneficial to the future combustion experiments in space.
Peer Review Status:Awaiting Review
Subjects: Geosciences >> Space Physics submitted time 2016-05-13
Abstract： After lots of experiments by using 19~27MeV differential energetic proton data based on the observation of SAMPEX from July of 1992 to June of 2004, it is found that the change of F_(10.7) and altitude have a great influence on the distribution of differential energetic proton flux in South Atlantic Anomaly. During the geomagnetic quiet time at 54025km altitude, the energetic proton flux in South Atlantic Anomaly decreased with the increasing of F_(10.7), and the variation trend was flat when F10.7 ≥ 115 sfu. It is found that there was obviously an anti-correlation between the absolute value of SYM-H and the differential energetic proton flux in South Atlantic Anomaly for storms with SYM-H ? -50, and also there was a lasting effect on differential energetic proton flux in South Atlantic Anomaly. In addition, the proton flux could be significantly reduced in South Atlantic Anomaly during the main phase, while the proton flux showed a substantial resuming trend in the recovery phase of geomagnetic storms.
Peer Review Status:Awaiting Review
Subjects: Geosciences >> Space Physics submitted time 2016-05-13
Abstract： Sprites are the transient luminous events above very active thunderstorms and are the direct evidence of the energy in troposphere coupled to the upper atmosphere. The emissive spectrum study is the important means to understand the energy injected into upper atmosphere and regional ionization, the electron energy distribution during the whole event. These parameters are useful for the study of sprites' physical mechanism, in addition as a kind of natural atmospheric luminous phenomenon, the emissive spectrum study is useful for providing important information to the research of atmospheric radiation background information. Based on the Boltzmann Equation to calculate the time evolution of the electron energy distribution function in a mixture of partially ionized gases with an applied electric field, the paper calculated the spectral intensity in typical emissive band for sprites. Simulation results show that the emissive intensity is more intensive with more intensive E/N and the emissive spectrum is from far ultraviolet to near infrared.
Peer Review Status:Awaiting Review
Subjects: Geosciences >> Space Physics submitted time 2016-05-13
Abstract： The technology of far ultraviolet photon-counting imaging detection is to record each single photon position and achieve the purpose of general imaging by detecting weak single photon information. The counting rate limits the information acquisition. On the basis of analyzing factors affecting the counting rate, the front-end analog circuit is needed for the amplification and shaping of the detector signals. Eventually, A225 chip was chosen as the pre-amplifier and shaping circuit was designed in the analog front-end circuit. Corresponding simulation and experimental results show that the circuit design is reasonable, and the counting rate can reach 200 kHz.
Peer Review Status:Awaiting Review
Subjects: Geosciences >> Space Physics submitted time 2016-05-13
Abstract： The outer radiation belt consists mainly of high energy electrons trapped by the Earth's magnetic field. The disturbance of the geomagnetic field caused by the Coronal Mass Ejection (CME) or the Co-rotating Interaction Region (CIR) can result in electron radiation belt variations. According to the variation feature of high energy electron flux in the outer radiation belt during magnetic storms, a novel index referred to as high electron flux fluctuation index was evaluated by using the 5-min resolution sampled electron flux data provided by GOES, and its correlation with geomagnetic Kp index was analyzed. It is found that high electron flux fluctuation index has a good correlation with geomagnetic Kp index, and the new index can be used as an indicator of geomagnetic storm occurrence. In comparison with 3-hour Kp index, which is wildly used in space environment operation prediction system, the suggested index in this paper can alert geomagnetic storm occurrence earlier.
Peer Review Status:Awaiting Review
Subjects: Geosciences >> Space Physics submitted time 2016-05-13
Abstract： The Reverse Monte Carlo (RMC) method is a powerful biasing technique available in Geant 4, also known as the Adjoint Monte Carlo method. In this method, particles are generated on the external boundary of the sensitive part of the geometry and then tracked backward in the geometry till they reach the external source surface, or exceed an energy threshold. By this way the computing time is focused only on particle tracks that are contributing to the tallies. The RMC method is much rapider than the Forward Monte Carlo (FMC) method when the sensitive part of the geometry is smaller compared to the rest of the geometry as well as the external source. Compared with the FMC method, accuracy of the RMC method applied to the radiation dose of the satellite is verified. Comparisons of RMC with the SHIELDOSE2, SSAT show that RMC is the preferred method of high-precision satellite radiation dose.
Peer Review Status:Awaiting Review
Subjects: Geosciences >> Space Physics submitted time 2016-05-13
Abstract： Effects of the nonuniform feedback magnetic field on the fluxgate sensor is studied, and several typical types of the sensor are analyzed and compared mutually. It is required that the drive cores of fluxgate sensor should work in a uniform magnetic field in principle. When the magnetic field is nonuniform, error signal will be caused. Resultingly, the nonuniformity of the feedback magnetic field will lead to the change of fluxgate sensor's linear coefficient. Typical types of fluxgate sensors which work for space magnetic exploration include discrete form, Helmholtz form and Compacted Spherical Configuration (CSC) form, etc. The nonuniformity of the three feedback coils are analyzed as well as the performance of the fluxgate sensor when the feedback magnetic field is nonuniform. Compared to the simulation results, uniformity and stability of CSC sensor are much better than that of the discrete sensor, and CSC sensor is more conducive to the space magnetic field detection.
Peer Review Status:Awaiting Review
Subjects: Geosciences >> Space Physics submitted time 2016-05-13
Abstract： A kind of front-end signal processing circuit of the electric field instrument, which would be used in the Earth's magnetosphere measurement, is investigated and presented in this work. The double-probe electric field instrument outputs drive current to the ambient plasma environment, and measures the potential difference between the two probes to detect the electric field. Plasma impedance of the magnetosphere is high, so the probe of the electric field instrument will operate in a high voltage to match the electric current requirement. When the operating voltage is close to or surpasses the circuit threshold voltage, the measuring results would be affected, and the instrument will be possibly damaged. This paper adopts voltage scheme with low bias current and feedback floating power supply control scheme, to solve the weak current sampling problem and high dynamic potential handling problem in measuring the electric field of a thin plasma. Test results show that the circuit can make the probe adapt to the floating ground in the dynamic voltage range of 100 V, and measure the electric field from DC to 150kHz, with a low noise level below 14nV?mHz~(-1/2), which meets the needs of electric field measurements in magnetosphere.
Peer Review Status:Awaiting Review
Subjects: Geosciences >> Space Physics submitted time 2016-05-13
Abstract： The nightly and seasonal variability of gravity wave activity and spectra in the mesopause over Beijing are studied with 3 years of sodium lidar observations. From the linear layer density response to gravity wave forcing, the lidar data were analyzed to get the atmospheric density perturbations and their spectra. The atmospheric density perturbation, density variance for fluctuations with vertical scales between 2 and 10 km, and amplitudes of density perturbation spectra at m = 2pi/8, 2pi/4, m = 2pi/1.5, m = 2pi/1,and omega = 2pi/60,omega = 2pi/40,2pi/25 all exhibit large nightly variability as well as large seasonal variations, with the semiannual maxima occurring near the solstice. The mean RMS atmospheric density perturbation over Beijing are 5.8%, which are obviously larger in summer than that in winter and the maxima occur near the solstice. The m spectra show power law shapes, and their range of variation is between -1.97 and -3.67 with an annual mean value of -3.02, and omega spectra is between -1.06 and -2.08 with an annual mean value of -1.92, respectively. It is concluded that the reaction of the Qinghai-Tibet Plateau and the background wind may be the main reason of the gravity wave behaviors at Beijing.
Peer Review Status:Awaiting Review
Subjects: Geosciences >> Space Physics submitted time 2016-05-13
Abstract： The unique combination of global coverage, high precision, high vertical resolution, long-term stability and all-weather viewing of radio occultation will enhance the data sets of numerical weather prediction and improve the precision of Numeric Weather Prediction (NWP). And data assimilation requires preprocessing of the raw radio signals into the bending angles and refractivity. Then the atmospheric parameters such as temperature, pressure and humidity can be retrieved through data variational assimilation. The procedures for processing of radio occultation data, especially several important steps are introduced. And comparative analysis between these results and those from CDAAC shows that below the altitude of 30 km, the relative errors of refractivity, pressure and humidity are within 2% and the deviation of temperature is below 2K. The results are also compared with the data from ERA-interim model of ECMWF and similar conclusion is obtained.
Peer Review Status:Awaiting Review
Subjects: Geosciences >> Space Physics submitted time 2016-05-13
Abstract： Russia's Mars probe Phobos-Grunt together with China's first Mars probe Yinghuo-1 were launched into Low Earth Orbit (LEO) on November 9, 2011. Unfortunately, the main probe failed to fire its thrusters and transfer its orbit as planned after 159 minutes, eventually the trip to Mars was terminated. The most likely cause of the accident investigated by Russian Space Agency (RSA) was that RAM chips in onboard control computers worked wrong when hit by cosmic heavy charged particles, which sequently led to the two computers restart and eventually disturbed the probe totally. However experts on satellite radiation hardness casted lot of doubt on the statement that LEO probe can be effected by Single-Event Effects (SEE) resulting from space radiation particles in so short period of time. Based on information of the victim RAM components disclosed by RSA, experiment tests and calculations were performed for K6R4016V1D chip to predict SEE rate when applied in LEO. Finally, possibility for SEE to cause the failure of Phobos-Grunt probe was discussed.
Peer Review Status:Awaiting Review
Subjects: Geosciences >> Space Physics submitted time 2016-05-13
Abstract： FY-3A satellite can measure the radiation dose data from different directions during the missions from 2008 to 2012. In this paper, we describe total radiation dose from two directions, and dose rate variation with energetic particle flux. The result shows that different sections of the spacecraft receive different amounts of radiation dose, which is always consistent with space distribution of energetic particles. Absorbed dose rate changed greatly from several rad (Si).d~(-1) during quite time to even more than tenfold during disturbances. The increased high energy electrons in polar regions during disturbances are responsible for significant increase of radiation dose. At last, FY-3A radiation dose during the operational period of the mission is compared with the results calculated by SPENVIS. It is obvious that observation data is more realistic to reflect the real space radiation environment.
Peer Review Status:Awaiting Review
Subjects: Geosciences >> Space Physics submitted time 2016-05-13
Abstract： Combining with Nakagami fading channel model,Rayleigh channels and Rician channels were analyzed between sounding rockets and ground station during the flight course.It takes an example of a variable modulation system with four types of modulations,including BPSK,QPSK,16QAM and 64QAM,and proposes a method to acquire the optimum signal-to-noise ratio switch threshold,according to different elevation angles of ground receiving station. The optimum threshold could maximize the throughput,while satisfying BER goal.Furthermore, the paper analyzes and compares the throughput difference with optimum signal-to-noise ratio switch threshold,BPSK modulation method and constant-BER signal-to noise ratio threshold. The results show that,by adoption of the optimum threshold,system throughput is 3.89 times and 1.043 times higher than the other two methods,respectively. The results could provide reference and basis for the application of variable modulation technology into practical sounding rockets projects.
Peer Review Status:Awaiting Review
Subjects: Geosciences >> Space Physics submitted time 2016-05-13
Abstract： To solve the problem that data handling system for sounding rockets lacks feasibility, and increasing requirements on expansibility and reliability of data handling system, a general and extensible data handling system is proposed. This system uses TMS570LS3137 produced by TI as CPU, and has abundant interfaces, such as IIC, CAN, Ethernet and SD card. EMIF interface provides external modules with addressing space. For software, muC/OS-II is ported to system and combines with drivers to complete invoking multitask. This system can satisfy various testing task and has high value in aerospace applications.
Peer Review Status:Awaiting Review
Subjects: Geosciences >> Space Physics submitted time 2016-05-13
Abstract： GMSK modulation plays an important role in space telecommunications. Local oscillator phase noise has significant influence on GMSK demodulation system. Some characteristics of phase noise and its math expressions on both time and frequency domains are analyzed. Furthermore, the simulated phase noise sequence is added to the GMSK modulation system to show how the different levels of phase noise affect the demodulation performance. The conclusions have deep reference value to optimize the GMSK demodulation system. This method to analyze phase noise and its effect can be extended to any modulation system.
Peer Review Status:Awaiting Review
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