北斗星基增强电离层模型精度评估与分析

针对如何有效地对北斗星基增强系统(SBAS)电离层在模型精度、模型时效性等方面进行综合评估,提出了一种修正的CODE格网模型,通过增加国内陆态网监测站观测数据,提升了CODE格网模型精度。以此模型为基准,利用2020年近一个月的数据分析了北斗区域格网电离层模型和北斗SBAS电离层模型的延迟误差、改正比例的变化以及在全球的覆盖范围,并从全球不同纬度带比较了北斗基本导航和星基增强电离层模型的精度。结果表明修正的CODE模型精度符合评估要求,且与我国电离层实际变化情况更吻合,北斗区域格网电离层模型和北斗SBAS电离层模型精度相当,优于0.3m,改正比例均优于80%,但北斗SBAS电离层模型覆盖范围明显更大。     

On the behavior of thermospheric O1D 630.0 nm dayglow emission during counter electrojet events

This study presents the response of thermospheric O¹D 630.0 nm dayglow emission to the variability associated with equatorial Counter Electrojet (CEJ) events. The analysis based on the data from a meridian scanning Dayglow Photometer, Digital Ionosonde and Proton Precession Magnetometer over Trivandrum (8.5°N, 77°E, 0.5°dip lat.), indicates that the O¹D 630.0 nm emission behave distinctly different during the CEJ events compared to that on normal days. It has been observed that O¹D 630.0 nm emission shows enhancement during the negative excursion of the ΔH, followed by an unusual depletion during the peak CEJ time. The observed variability was found to be more pronounced in a latitudinal region of ±3° centered at around the dip equator. In addition, the emission intensities also exhibit the presence of enhanced short period oscillations of periodicity 20–30 min during the CEJ events. Analysis of the data from the collocated ionosonde revealed that the F-region electron density showed enhancement during the early phase of the CEJ and a decrease during the peak CEJ. Further, the simulation studies using a Quasi 2 dimensional ionospheric model showed that the modified plasma fountain during the CEJ can alter the plasma density at the emission centroid. The study reveals a strong dynamical coupling between the E and F-region of the dip equatorial ionosphere.     

不同基准钟对BDS实时钟差估计的影响分析CSCD

BDS原始观测量是站星之间的相对时间延迟,在实时卫星钟差估计过程中需要引入一个基准钟,求解该基准约束下的钟差产品。基于两种不同的基准约束条件实时估计BDS卫星钟差,并从实时钟差的估计精度、钟差频率特性(频率漂移率、频率准确度、频率稳定度)及钟差预报精度等方面分析其对BDS实时钟差估计的影响。算例结果表明,在两种不同的基准模式下,估计得到的BDS实时卫星钟差性能基本一致,在实际使用中可根据情况采用不同的基准钟进行钟差估计,为BDS实时卫星钟差估计时基准钟的选择提供了参考。     

The global response of terrestrial ionosphere to the December 2015 space weather event

This paper investigates the ionospheric storm of December 19–21, 2015, which was initiated by two successive CME eruptions that caused a G3 space weather event. We used the in situ electron density (N_e) and electron temperature (T_e) and the Total Electron Content (TEC) measurements from SWARM-A satellite, as well as the O/N₂ observations from TIMED/GUVI to study the ionospheric impact. The observations reveal the longitudinal and hemispherical differences in the ionospheric response to the storm event. A positive ionospheric storm was observed over the American, African and Asian regions on 20 December, and the next day showed a negative storm. Both these exhibited hemispheric differences. A positive storm was observed over the East Pacific region on 21 December. It is seen that the net effect of both the disturbance dynamo electric field and composition differences become important in explaining the observed variability in topside ionospheric densities. In addition, we also discuss the T_e variations that occurred as a consequence of the space weather event.