共查询到20条相似文献，搜索用时 31 毫秒
1.
区别于以往GPS电离层层析研究主要关注迭代模型的思路,本文从两方面入手提高GPS电离层层析迭代算法的反演精度:一方面,顾及传统电离层层析迭代模型仅与对电子密度误差起放大作用的GPS射线截距权重相关的不足,提出考虑层析像素格网中的电子密度对GPS TEC的贡献建立新的迭代模型,在不同电子密度像素格网内重新分配GPS TEC实测值与其反演值之间的差距;另一方面,顾及电离层层析迭代算法中松弛因子对反演结果的影响,提出考虑电子密度变化构造新的松弛因子,抑制传播噪声对电子密度反演精度的影响.实验结果显示,相对于传统代数重构算法(ART),新方法反演的电离层电子密度剖面更接近于电离层测高仪观测的电子密度剖面,提高了电子密度反演精度. 相似文献
2.
When travelling through the ionosphere the signals of space-based radio navigation systems such as the Global Positioning System (GPS) are subject to modifications in amplitude, phase and polarization. In particular, phase changes due to refraction lead to propagation errors of up to 50 m for single-frequency GPS users. If both the LI and the L2 frequencies transmitted by the GPS satellites are measured, first-order range error contributions of the ionosphere can be determined and removed by difference methods. The ionospheric contribution is proportional to the total electron content (TEC) along the ray path between satellite and receiver. Using about ten European GPS receiving stations of the International GPS Service for Geodynamics (IGS), the TEC over Europe is estimated within the geographic ranges –20° 40°E and 32.5° ø 70°N in longitude and latitude, respectively. The derived TEC maps over Europe contribute to the study of horizontal coupling and transport processes during significant ionospheric events. Due to their comprehensive information about the high-latitude ionosphere, EISCAT observations may help to study the influence of ionospheric phenomena upon propagation errors in GPS navigation systems. Since there are still some accuracy limiting problems to be solved in TEC determination using GPS, data comparison of TEC with vertical electron density profiles derived from EISCAT observations is valuable to enhance the accuracy of propagation-error estimations. This is evident both for absolute TEC calibration as well as for the conversion of ray-path-related observations to vertical TEC. The combination of EISCAT data and GPS-derived TEC data enables a better understanding of large-scale ionospheric processes. 相似文献
3.
《Journal of Atmospheric and Solar》1999,61(16):1205-1218
The accuracy of single-frequency ocean altimeters benefits from calibration of the total electron content (TEC) of the ionosphere below the satellite. Data from a global network of Global Positioning System (GPS) receivers provides timely, continuous, and globally well-distributed measurements of ionospheric electron content. For several months we have been running a daily automatic Global Ionospheric Map process which inputs global GPS data and climatological ionosphere data into a Kalman filter, and produces global ionospheric TEC maps and ocean altimeter calibration data within 24 h of the end-of-day. Other groups have successfully applied this output to altimeter data from the GFO satellite and in orbit determination for the TOPEX/Poseidon satellite. Daily comparison of the global TEC maps with independent TEC data from the TOPEX altimeter is performed as a check on the calibration whenever the TOPEX data are available. Comparisons of the global TEC maps against TOPEX data will be discussed. Accuracy is best at mid-to-high absolute latitudes (∣latitude∣>30°) due to the better geographic distribution of GPS receivers and the relative simplicity of the ionosphere. Our highly data-driven technique is relatively less accurate at low latitudes and especially during ionospheric storm periods, due to the relative scarcity of GPS receivers and the structure and volatility of the ionosphere. However, it is still significantly more accurate than climatological models. 相似文献
4.
The measurements of an increase in the total electron content (TEC) of the ionosphere during solar flares, obtained based
on the GPS data, indicated that up to 30% of TEC increments corresponded to the ionospheric regions above 300 km altitude
in some cases, and TEC increased mainly below altitudes of 300 km in other cases. The theoretical model of the ionosphere
and plasmasphere was used to study the obtained effects. The altitude-time variations in the charged particle density in the
ionospheric region from 100 to 1000 km were used depending on the solar flare spectrum. An analysis of the modeling results
indicated that an intensification of the flare UV emission in the 55–65 and 85–95 nm spectral ranges results in a pronounced
increase in the electron density in the topside ionosphere (above 300 km). The experimental dependences of the ionospheric
TEC response amplitude on the localization and peak power of flares on the Sun in the X-ray range, obtained based on the GPS
data, are also presented in the work. 相似文献
5.
《Journal of Atmospheric and Solar》2007,69(15):1842-1850
Global positioning system (GPS) networks have provided an opportunity to study the dynamics and continuous changes in the ionosphere by supplementing ionospheric studies carried out using various techniques including ionosondes, incoherent scatter radars and satellites. Total electron content (TEC) is one of the physical quantities that can be derived from GPS data, and provides an indication of ionospheric variability. This paper presents a feasibility study for the development of a Neural Network (NN) based model for the prediction of South African GPS derived TEC. Three South African locations were identified and used in the development of an input space and NN architecture for the model. The input space included the day number (seasonal variation), hour (diurnal variation), Sunspot Number (measure of the solar activity), and magnetic index (measure of the magnetic activity). An analysis was done by comparing predicted NN TEC with TEC values from the IRI-2001 version of the International Reference Ionosphere (IRI), validating GPS TEC with ionosonde TEC (ITEC) and assessing the performance of the NN model during equinoxes and solstices. For this feasibility model, GPS TEC was derived for a limited number of years using an algorithm still in the early phases of validation. However, results show that NNs predict GPS TEC more accurately than the IRI at South African GPS locations, but that more good quality GPS data is required before a truly representative empirical GPS TEC model can be released. 相似文献
6.
The earlier experiments of ionospheric tomography were conducted by receiving satellite signals from ground-based stations and then reconstructing electron density distribution from measures of the total electron content (TEC). In June 1994, National Central University built up the low-latitude ionospheric tomography network (LITN) including six ground stations spanning a range of 16.7° (from 14.6°N to 31.3°N) in latitude within 1° of 121°E longitude to receive the naval navigation satellite system (NNSS) signals (150 and 400 MHz). In the study of tomographic imaging of the ionosphere, TEC data from a network of ground-based stations can provide detailed information on the horizontal structure, but are of restricted utility in sensing vertical structure. However, an occultation observation mission termed the global positioning system/meteorology (GPS/MET) program used a low Earth orbiting (LEO) satellite (the MicroLab-1) to receive multi-channel GPS carrier phase signals (1.5 and 1.2 GHz) and demonstrate active limb sounding of the Earth's atmosphere and ionosphere. In this paper, we have implemented the multiplicative algebraic reconstruction technique (MART) to reconstruct and compare two-dimensional ionospheric structures from measured TECs through the receptions of the GPS signals, the NNSS signals, and/or both of the systems. We have also concluded the profiles retrieved from tomographic reconstruction showing much reasonable electron density results than the original vertical profiles retrieved by the Abel transformation and being in more agreement in peak electron density to nearby ionosonde measurements. 相似文献
7.
I. E. Zakharenkova Iu. V. Cherniak I. I. Shagimuratov M. V. Klimenko 《Geomagnetism and Aeronomy》2018,58(1):70-82
The dynamic picture of the response of the high- and mid-latitude ionosphere to the strong geomagnetic disturbances on March 17–18, 2015, has been studied with ground-based and satellite observations, mainly, by transionospheric measurements of delays of GPS (Global Positioning System) signals. The advantages of the joint use of ground-based GPS measurements and GPS measurements on board of the Swarm Low-Earth-Orbit satellite mission for monitoring of the appearance of ionospheric irregularities over the territory of Russia are shown for the first time. The results of analysis of ground-based and space-borne GPS observations, as well as satellite, in situ measurements, revealed large-scale ionospheric plasma irregularities observed over the territory of Russia in the latitude range of 50°–85° N during the main phase of the geomagnetic storm. The most intense ionospheric irregularities were detected in the auroral zone and in the region of the main ionospheric trough (MIT). It has been found that sharp changes in the phase of the carrier frequency of the navigation signal from all tracked satellites were recorded at all GPS stations located to the North from 55° MLAT. The development of a deep MIT was related to dynamic processes in the subauroral ionosphere, in particular, with electric fields of the intense subauroral polarization stream. Analysis of the electron and ion density values obtained by instruments on board of the Swarm and DMSP satellites showed that the zone of highly structured auroral ionosphere extended at least to heights of 850–900 km. 相似文献
8.
基于GNSS(Global Navigation Satellite Systems)的发展,我们利用具有北斗、GLONASS和GPS三系统信号接收功能的接收机观测的数据,结合电离层总电子含量(Total Electron Content, TEC)的反演算法,提取出GNSS三系统观测的电离层TEC;同时,将GNSS三系统获取的TEC应用到电离层TEC地图、行进式扰动、不规则体结构和电离层的太阳耀斑响应等方面的研究中,这也是首次使用三种GNSS系统数据对电离层进行联合探测研究.研究结果表明,增加了北斗系统的GNSS三系统在研究中国地区电离层TEC地图、周日变化、逐日变化,行进式扰动以及电离层的实时监测等方面较单系统的GPS具有明显的优势. 相似文献
9.
GPS无线电掩星技术是崭新的、高效的地球大气层和电离层探测技术,但仍在发展和完善之中.本文详细推导了Abel积分和绝对TEC电离层反演方法,研究了如何解决Abel积分产生的上下限异常问题;用COSMIC发布的GPS原始数据进行了反演计算,将结果与地面电离层测高仪数据进行了比较,最后讨论了周跳对反演结果的影响问题.结果表明：（1）在较高轨道高度（约800 km）,Abel积分与绝对TEC方法的反演结果基本一致,都与电离层测高仪反演结果符合良好;在较低轨道高度（约500 km）,绝对TEC反演精度优于Abel积分反演精度;（2）绝对TEC反演的最大电子密度Nm较Abel积分法获得的结果更接近于电离层测高获得的峰值电子密度NmF2,绝对TEC反演法更加严密和有效;（3）周跳对绝对TEC反演结果的影响较Abel积分反演结果的影响更为敏感,但无论哪种方法,周跳对反演精度都造成严重损失.综合而言,绝对TEC反演法是更优的方法. 相似文献
10.
《Journal of Atmospheric and Solar》1999,61(16):1227-1236
Dual-frequency transmissions from the Global Positioning System satellites can be used to measure and map ionospheric total electron content (TEC) on global scales. Using data exclusively from ground-based GPS networks, global ionosphere mapping has been successfully applied using either two- or three-dimensional techniques. Two-dimensional TEC maps retrieve a horizontally-varying distribution of total electron content, assuming a fixed vertical electron density profile. In three-dimensional mapping, both the horizontal and vertical distribution density are adjusted to fit the data. We describe a three-dimensional TEC mapping algorithm that uses three independent constant-density slabs stacked vertically to model the electron density, and compare with a more conventional two-dimensional approach using a single slab. One apparent benefit of the new method is reduction in a level error of the TEC maps, which decreased by 1.7 TECU using the three-dimensional retrieval on simulated data (1 TEC Unit corresponds to 1016 electrons/m2). Another benefit of the multilayer approach is improved slant TEC modeling. Using actual data from an equatorial site at Cocos Islands (96.8E, 12.2 S), three slab modeling improved estimates of slant TEC by a factor of 2 for elevation angles between 10 and 20° (9 versus 4.4 TECU, root-mean-square). However, the global structure of the vertical TEC retrievals we analyzed did not improve using three-dimensional modeling. This may be due to a critical approximation shared by both techniques that TEC persists unchanged at a given local time. This assumption is required to produce global maps from observations acquired from widely scattered ground receivers. Further improving the retrieval of global TEC structure with ground-based data probably requires improved dynamical models of TEC behavior. New data available from GPS receivers in low Earth orbit is also promising. 相似文献
11.
Tamara L. Gulyaeva 《Acta Geophysica》2007,55(2):253-266
Variations of the upper boundary of the ionosphere (UBI) are investigated based on three sources of information: (i) ionosonde-derived
parameters: critical frequency foF2, propagation factor M3000F2, and sub-peak thickness of the bottomside electron density profile; (ii) total electron content (TEC) observations from signals
of the Global Positioning System (GPS) satellites; (iii) model electron densities of the International Reference Ionosphere
(IRI*) extended towards the plasmasphere. The ionospheric slab thickness is calculated as ratio of TEC to the F2 layer peak electron
density, NmF2, representing a measure of thickness of electron density profile in the bottomside and topside ionosphere eliminating the
plasmaspheric slab thickness of GPS-TEC with the IRI* code. The ratio of slab thickness to the real thickness in the topside ionosphere is deduced making use of a similar ratio
in the bottomside ionosphere with a weight Rw. Model weight Rw is represented as a superposition of the base-functions of local time, geomagnetic latitude, solar and magnetic activity.
The time-space variations of domain of convergence of the ionosphere and plasmasphere differ from an average value of UBI
at ∼1000 km over the earth.
Analysis for quiet monthly average conditions and during the storms (September 2002, October–November 2003, November 2004)
has shown shrinking UBI altitude at daytime to 400 km. The upper ionosphere height is increased by night with an ‘ionospheric
tail’ which expands from 1000 km to more than 2000 km over the earth under quiet and disturbed space weather. These effects
are interposed on a trend of increasing UBI height with solar activity when both the critical frequency foF2 and the peak height hmF2 are growing during the solar cycle. 相似文献
12.
The computerized ionospheric tomography is a method for imaging the Earth’s ionosphere using a sounding technique and computing the slant total electron content (STEC) values from data of the global positioning system (GPS). The most common approach for ionospheric tomography is the voxel-based model, in which (1) the ionosphere is divided into voxels, (2) the STEC is then measured along (many) satellite signal paths, and finally (3) an inversion procedure is applied to reconstruct the electron density distribution of the ionosphere. In this study, a computationally efficient approach is introduced, which improves the inversion procedure of step 3. Our proposed method combines the empirical orthogonal function and the spherical Slepian base functions to describe the vertical and horizontal distribution of electron density, respectively. Thus, it can be applied on regional and global case studies. Numerical application is demonstrated using the ground-based GPS data over South America. Our results are validated against ionospheric tomography obtained from the constellation observing system for meteorology, ionosphere, and climate (COSMIC) observations and the global ionosphere map estimated by international centers, as well as by comparison with STEC derived from independent GPS stations. Using the proposed approach, we find that while using 30 GPS measurements in South America, one can achieve comparable accuracy with those from COSMIC data within the reported accuracy (1 × 1011 el/cm3) of the product. Comparisons with real observations of two GPS stations indicate an absolute difference is less than 2 TECU (where 1 total electron content unit, TECU, is 1016 electrons/m2). 相似文献
13.
本文利用设在武汉(11436°E,3053°N,磁纬194°)的GPS电离层TEC和电波闪烁监测仪的测量数据，分析了2004年11月强磁暴期间TEC的响应以及电波闪烁和TEC起伏的特征.结果表明，在这次强磁暴期间，武汉及其邻近地区电离层TEC的响应以正暴相为主，正暴相分别出现在两次主相期间，最大正偏离达到50 TECU.这次磁暴另一个重要影响是主相期间L波段振幅闪烁的活动性及其强度显著增强.S4指数最大接近10.伴随增强的闪烁活动，多次观测到深度耗尽的等离子体泡与TEC起伏，TEC变化率的标准差ROTI指数也显著增强.分析揭示， ROTI指数与S4指数呈正相关，相关系数达到097.线性回归计算得到，ROTI和S4的比率为964. 相似文献
14.
《Journal of Atmospheric and Solar》2007,69(13):1587-1598
In this paper, we investigate the solar flare effects of the ionosphere at middle latitude with a one-dimensional ionosphere theoretical model. The measurements of solar irradiance from the SOHO/Solar EUV Monitor (SEM) and GOES satellites have been used to construct a simple time-dependent solar flare spectrum model, which serves as the irradiance spectrum during solar flares. The model calculations show that the ionospheric responses to solar flares are largely related to the solar zenith angle. During the daytime most of the relative increases in electron density occur at an altitude lower than 300 km, with a peak at about 115 km, whereas around sunrise and sunset the strongest ionospheric responses occur at much higher altitudes (e.g. 210 km for a summer flare). The ionospheric responses to flares in equinox and winter show an obvious asymmetry to local midday with a relative increase in total electron content (TEC) in the morning larger than that in the afternoon. The flare-induced TEC enhancement increases slowly around sunrise and reaches a peak at about 60 min after the flare onset. 相似文献
15.
V. L. Khalipov A. E. Stepanov G. A. Kotova S. E. Kobyakova V. V. Bogdanov A. B. Kaisin V. A. Panchenko 《Geomagnetism and Aeronomy》2016,56(5):535-544
Vertical and horizontal plasma drifts are investigated during the polarization jet (PJ) detection in the F2 ionospheric layer based on the Doppler measurements at the Yakutsk meridian chain of subauroral ionospheric stations. It is shown that the velocities of vertical and horizontal drifts are significantly higher than the background motion during PJ observation periods. The ionospheric plasma motion direction changes from upward to downward on the polar edge of the main ionospheric trough. Doppler measurements on the DPS-4 ionosondes are compared with the simultaneous measurements of the plasma drift on the DMSP satellites during their passage near the Yakutsk meridian. The two kinds of measurements are in good agreement with each other. During the magnetic storm of June 23, 2005, by measurements of the DMSP satellites, the velocities of upward plasma flows were 1.0–1.4 km/s at a satellite altitude of 850 km. In the ionospheric F region, this speed corresponds to 150 m/s. According to satellite measurements, the westward drift velocity reached 2.5 km/s. The development of the polarization jet in the ionosphere was accompanied by a tenfold decrease in the electron density in 15–30 min. 相似文献
16.
利用GPS计算TEC的方法及其对电离层扰动的观测 总被引：36，自引：8，他引：28
在总结用ＧＰＳ研究电离层电子总量ＴＥＣ的数据处理方法基础上,分析了利用伪距观测量和载波相位观测量计算电离层ＴＥＣ的特点及误差来源．在处理过程中考虑了卫星的硬件延迟偏差,分析了应用ＩＲＩ模型进行接收机硬件延迟偏差修正的可能性,发现利用少量ＧＰＳ数据和ＩＲＩ模型修正接收机硬件延迟偏差有一定的困难．最后,利用一些ＧＰＳ观测数据有针对性地研究了电离层对若干次扰动事件的响应．包括一次大的太阳耀斑期间的电离层ＴＥＣ变化、一次较典型的电离层行扰以及日食期间的电离层ＴＥＣ的相对变化等电离层物理问题．结果表明,利用该方法计算ＴＥＣ的精度可满足电离层扰动现象的研究． 相似文献
17.
《Journal of Atmospheric and Solar》2008,70(15):1919-1928
This paper investigates the features of pre-earthquake ionospheric anomalies in the total electron content (TEC) data obtained on the basis of regular GPS observations from the International GNSS Service (IGS) network. For the analysis of the ionospheric effects of the 26 September 2005 Peru earthquake, Global Ionospheric Maps (GIMs) of TEC were used. The possible influence of the earthquake preparation processes on the main low-latitude ionosphere peculiarity—the equatorial anomaly—is discussed. Analysis of the TEC maps has shown that modification of the equatorial anomaly occurred a few days before the earthquake. In previous days, during the evening and night hours (local time—LT), a specific transformation of the TEC distribution had taken place. This modification took the shape of a double-crest structure with a trough near the epicenter, though usually in this time the restored normal latitudinal distribution with a maximum near the magnetic equator is observed. Additional measurements (CHAMP satellite) have also confirmed the presence of this structure. To compare the vertical TEC measurements obtained with GPS satellite signals (GPS TEC), the International Reference Ionosphere, IRI-2001, was used for calculating the IRI TEC. 相似文献
18.
Ping Yin Cathryn N. Mitchell Lucilla Alfonsi Mike Pinnock Paul Spencer Giorgiana De Franceschi Vincenzo Romano Patrick Newell Pierguido Sarti Monia Negusini Alessandro Capra 《Journal of Atmospheric and Solar》2009,71(17-18):1757-1765
Ground-based dual-frequency GPS observations can be used to create images of electron density. This is well established for the Arctic ionosphere; here one of the first results is presented for the Antarctic. In this study, the GPS receivers in the Antarctic are supplemented with another GPS receiver onboard CHAMP. The aim of the study is to demonstrate the technique for investigating geophysical events, for example, an ionospheric disturbance period on 11 February 2004. The images have been validated by in-situ measurements from DMSP and CHAMP satellites, as well as Super Dual Auroral Radar Network (SuperDARN) convection patterns, which are able to confirm the location, presence, and transportation of large-scale plasma patches. This study indicates that although the convection still dominates in the high-latitude ionosphere, soft precipitation within the polar cap may play a role in the evolution of the polar patches. It also illustrates the potential for future multi-instrument studies of the Antarctic. 相似文献
19.
利用上海地区GPS综合应用网提供的高时空分辨率的双频GPS观测资料,研究了该区域内一电离层不均匀体的产生、消亡过程.首先,采用Kalman滤波的方法改善双频伪距之差的观测精度,并利用参数估计的方法计算该时段内相应的硬件延迟.再根据电离层单层模型,利用GPS双频观测量、测站位置和GPS精密星历,求出GPS信号穿刺点的坐标和垂直方向电离层的电子含量;然后内插并获取其等值线图.等值线图随时间的变化表明,受等离子体湍流的影响,2003年9月8日北京时间9时40分左右在38°N、118°E左右产生了一电离层不均匀体,其尺度大约在50km左右,生存时间大约为5min.受地球重力场和高空风场的影响,该不均匀体向东北方向扩散.然后,利用大气扩散模型,按扩散方程计算分析了该不均匀体可能发生的电离层层区.理论计算表明,该不均匀体发生在电离层扩展F区,高度在350km左右. 相似文献
20.
利用GPS信标测量获得的电离层电子浓度总含量（TEC）是沿电波路径的斜向TEC.理论研究和实际应用中,常常需要通过映射函数将斜向TEC转换为垂直方向的TEC,这在当前主要采用对电子浓度分布模型的数值积分得到模型映射函数来实现.本文在考察现有不同模型映射函数的基础上,又提出了一种源于实际观测的实验映射函数的概念与估算方法.我们利用IGS的全球GPS观测站的斜向TEC和JPL提供的垂直TEC数据获得了2006年期间的实验映射函数,并对所得结果进行了初步统计分析.在卫星天顶角较小时,上述实验映射函数和模型映射函数之间相差甚微,均可很好描述垂直TEC与斜TEC之间关系;但卫星天顶角较大时,实验映射函数和常用的模型映射函数之间存在明显差异.本文认为,这种差异主要是因为现有模型映射函数中没有考虑到等离子体层的贡献.我们认为采用基于实验映射函数的模式,或者通过考虑等离子体层的贡献对现有模型映射函数进行改进,可以有效提高电离层TEC的估算精度. 相似文献