Variability study of ionospheric total electron content at crest of equatorial anomaly in China from 1997 to 2007

The variation of TEC data at Wuhan station (geographic coordinate: 30.5°N, 114.4°E; geomagnetic coordinate: 19.2°N, 183.8°E) at crest of equatorial anomaly in China from January 1997 to December 2007 were analyzed. Variability with solar activity, annual, semiannual, diurnal and seasonal variation were also analyzed. The MSIS00 model and ISR model were used to analyze the possible mechanisms of the variabilities found in the results. The TEC data in 1997 and 2001 deduced from another crest station Xiamen (geographic coordinate: 24.4°N, 118.1°E; geomagnetic coordinate: 13.2°N, 187.4°E) were used to contrast. Analysis results show that long-term variations of TEC at Xiamen station are mainly controlled by the variations of solar activities. Typical diurnal variation behaves as a minimum of the TEC in the pre-dawn hours around 05:00–06:00LT and a maximum on the afternoon hours around 13:00–15:00LT. Some features like the semiannual anomaly and winter anomaly in TEC have been reported. The anomaly may be the result of common action of the electric field over the magnetic equatorial and the [O/N₂] at the crest station.     

A preliminary study of the single crest phenomenon in total electron content (TEC) in the equatorial anomaly region around 120°E longitude between 1999 and 2012

The diurnal variations in total electron content (TEC) in the equatorial ionisation anomaly (EIA) region are not always represented by two crests on both sides of the magnetic equator. Sometimes, only an obvious single crest is evident at equatorial and low latitudes. In this paper, we focus on analysis of the morphological features of the single crest phenomenon in TEC around 120°E longitude during geomagnetic quiet days (Kp < 4₋). The variations in TEC are also compared with morphological parameters (foF2 and hmF2) derived from the International Reference Ionosphere extended to Plasmasphere (IRI–Plas) model. Our results show that the single crest phenomenon occurs mainly on days with extremely low solar activity, while the corresponding F2 layer critical frequency showed obvious asymmetry, or even only a single peak.     

利用IGS-TEC数据分析中国华南地区电离层赤道异常北驼峰的变化特征

利用2010年11月至2011年10月IGS提供的全球电子浓度总含量(TEC)数据, 分析太阳活动上升期华南地区(经度110°E, 纬度5°—35°N) 上空电离层赤道异常(EIA)北驼峰的变化特征. 结果显示, 电离层赤道异常北驼峰区TEC峰值I具有明显的季节和半年变化特征; 北驼峰峰值出现的时间T和纬度L的日变化有一个相对较大的变化区间, 其季节和半年变化特征并不明显; 太阳活动对北驼峰变化影响比较明显, 而地磁活动对北驼峰变化影响不明显.      

东亚大陆磁异常区地磁太阳日变化的异常特征

使用ＩＧＹ／ＩＧＣ（１９５７。７。１－１９５９。１２。３０）期间全球地磁台网和中国长春、北京、上海、拉萨四台的地磁资料，分析了东亚大陆磁常区地磁异常区地磁太阳静日变化Ｓｑ的异常特征，分析表明，组成Ｓｑ的两个主要谐波（１次和２次谐波）在东亚大陆常区呈现出不同于其他区的分布特征；Ｘ分量振幅值一般高于地磁纬度相同的其他地区的振幅。振幅极小值出现的纬度向南移动约２０°，极小值的量值小于其他地区，由东亚异常     

基于模糊数据挖掘的网络入侵检测模型

提出了一个基于模糊数据挖掘的入侵模型.异常检测的一个主要问题是正常模式随时间变化.如果一个实际的入侵行为稍有偏差就有可能与正常的模式相匹配,而异常检测系统则无法检测到这种入侵行为.为解决这个问题,本文利用模糊数据挖掘技术建立正常模式,并用一组模糊关联规则表示.在进行异常检测时,利用新的审计数据挖掘当前模糊关联规则,并计算其与正常模式的相似度,如相似度低于规定的阈值,使其产生入侵警报.最后,文中利用遗传算法优化模糊成员函数来选择其参数.     

赤道异常的行星波周期振荡的统计特征与逐年变化及其QBO调制

利用赤道异常峰区台站(Okinawa)观测的, f₀F₂资料(1977—1990), 分析计算了赤道电离层行星波周期振荡(2日、3—4日、5—7日及10—16日)的特征及其变化规律, 发现其在一年四季都有出现, 但相对强度在冬、夏季较大, 且冬季更强;其振荡周期也随季节有所变化, 以2日波而言, 夏季更接近于2日, 而冬季则多在2日多至2日半区间振荡;更长周期的波的所谓夏季峰值的出现, 还有向夏初和夏末过渡的趋势。并发现振荡与太阳活动性呈负相关, 即低年的相对幅度要强于高年, 并且周期越长负相关越显著;同时显示出振荡的出现率及频率变化受到QBO的调制, QBO东风相期间比西风相更易于出现长周期振荡。这些结果说明赤道电离层明显受到中低层大气动力学变化的向上耦合的影响。      

基于正反Kalman滤波的动基座重力仪数据处理方法

重力数据处理是动基座重力仪的核心技术,采用了一种基于正反Kalman滤波的数据处理方法提取重力异常值.以动基座重力仪(Sea and Air Gravity,SAG)为研究对象,根据系统参数推导了Kalman滤波方程,并运用正反Kalman滤波方法处理了SAG某飞行架次的数据.将提取的重力异常值与同机搭载飞行的俄罗斯高精度重力仪GT-1A的结果进行比对,试验结果表明,两者滤波结果差值的均方根误差要小于1 mGal.     

A simple and valid analysis method for orbit anomaly detection

A simple analysis method for orbit anomaly detection, called semi-major axis change method (SACM) was presented by using a relationship between the change of orbit parameters and velocity increments. In this method, the mean value and standard deviation of the semi-major axis change in different time intervals were first calculated according to historical data. Then, these two parameters, the mean value and standard deviation of the semi-major axis change, are chosen as basis variables and combined as an anomalous criterion. For orbit objects with different characteristic, anomalous thresholds were given in different time intervals for identifying the anomalies of the orbital objects. Finally, this method is used for low earth orbit (LEO) satellites and American–Russian breakup debris. By adopting this method, the characteristics of the orbit change were given. The accuracy rate of anomaly analysis for LEO satellites and American–Russian breakup debris can reach to 100%, which demonstrates that the method was rapid and valid.     

重力异常特征提取方法研究

将主元分析和独立分量分析相结合应用于重力异常信号的特征提取.采用主元分析对测量数据进行去相关和降维预处理,再利用独立分量分析算法提取重力信号的特征系数.结合重力异常变化与特征系数的关系,提出了应用特征量化参数表征重力异常信号变化程度的方法.基于实测的重力异常信号进行了仿真试验,试验结果表明,本文提出的特征量化参数能有效的反映重力异常的幅值变化程度.     

三轴惯性平台式航空重力仪机载重力测量试验研究

介绍了自主研制的GIPS-1A三轴惯性平台式航空重力仪的组成、工作流程及技术指标,并给出了机载重力测量试验系统的集成方法和数据处理方法.经实际机载航空重力重复线精度测试和试生产测试,重复线内符合精度优于0.6mGal@0.01Hz;与国际上性能优异的GT-2A重力仪相比,重复线符合度好,试生产交叉点总精度相当,且异常形...