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2.
The ionospheric eclipse factor method (IEFM) and its application to determining the ionospheric delay for GPS 总被引:4,自引:1,他引:3
A new method for modeling the ionospheric delay using global positioning system (GPS) data is proposed, called the ionospheric
eclipse factor method (IEFM). It is based on establishing a concept referred to as the ionospheric eclipse factor (IEF) λ
of the ionospheric pierce point (IPP) and the IEF’s influence factor (IFF) . The IEF can be used to make a relatively precise distinction between ionospheric daytime and nighttime, whereas the IFF
is advantageous for describing the IEF’s variations with day, month, season and year, associated with seasonal variations
of total electron content (TEC) of the ionosphere. By combining λ and with the local time t of IPP, the IEFM has the ability to precisely distinguish between ionospheric daytime and nighttime, as well as efficiently
combine them during different seasons or months over a year at the IPP. The IEFM-based ionospheric delay estimates are validated
by combining an absolute positioning mode with several ionospheric delay correction models or algorithms, using GPS data at
an international Global Navigation Satellite System (GNSS) service (IGS) station (WTZR). Our results indicate that the IEFM
may further improve ionospheric delay modeling using GPS data. 相似文献
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The annual and semi-annual variations of the ionosphere are investigated in the present paper by using the daytime F2 layer peak electron concentration (NmF2) observed at a global ionosonde network with 104 stations. The main features are outlined as follows. (1) The annual variations are most pronounced at magnetic latitudes of 40–60° in both hemispheres, and usually manifest as winter anomalies; Below magnetic latitude of 40° as well as in the tropical region they are much weaker and winter anomalies that are not obvious. (2) The semi-annual variations, which are usually peak in March or April in most regions, are generally weak in the near-pole regions and strong in the far-pole regions of both hemispheres. (3) Compared with their annual components, the semi-annual variations in the tropical region are more significant.In order to explain the above results, we particularly analyze the global atomic/molecular ratio of [O/N2] at the F2 layer peak height by the MSIS90 model. The results show that the annual variation of [O/N2] is closely related with that of NmF2 prevailing in mid-latitudes and [O/N2] annual variation usually may lead to the winter anomalies of NmF2 occurring in the near-pole region. Moreover, NmF2 semi-annual variations appearing in the tropical region also have a close relationship with the variation of [O/N2]. On the other hand, the semi-annual variations of NmF2 in the far-pole region cannot be simply explained by that of [O/N2], but the variation of the solar zenith angle may also have a significant contribution. 相似文献
5.
提出了一种精确估计区域北斗接收机硬件延迟(DCB)的方法。该方法不需要传统复杂的电离层模型,在已知一个参考站接收机硬件延迟的条件下,利用正常情况下电离层延迟量和卫星-接收机几何距离强相关这一特点,采用站间单差法来精确估计区域内BDS接收机的硬件延迟。试验结果表明,该方法单站估计的单站北斗接收机连续30d的硬件延迟RMS在0.3ns左右。通过GEO卫星双频观测值扣除已知卫星DCB和本文方法估计的接收机DCB,计算对应穿刺点一天的VTEC并和GIM格网内插结果并进行比对分析,二者大小和变化趋势均符合较好,进一步验证了本文提出的方法具有可靠性。 相似文献
6.
采用国际上广泛认可的高层大气和电离层经验模式提供的各种参数, 通过电离层电流连续方程, 计算出强磁暴条件下6月至日和12月至日内, 磁纬±72°和磁地方时00:00~24:00之间电离层电场、电流等的分布. 计算中考虑了地磁和地理坐标间的偏离; 除中性风场感生的发电机效应外, 还包含了磁层耦合(极盖区边界的晨昏电场和二区场向电流)的驱动外源. 结果表明, 6月至日时, 磁层扰动自极光区向中低纬的穿透情况在南、北半球内基本接近, 北半球内略强; 但12月至日时, 呈现明显的不对称性, 南半球的电流穿透远强于北半球, 而电场的穿透则是在北半球更强. 无论南北半球, 在中高纬地区, 午夜至黎明时段出现较强的东向电场分量, 其[WTHX]E×B[WTBZ]的向上漂移效应, 正是解释我们以往不少研究现象中所期盼的物理机制. 相似文献
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Ionospheric scintillation observations of VHF radio signals from FLEETSAT satellite (73°E longitude) at Bhopal from January
1990 to December 1990 have been used to study the characteristic variations of scintillation activity. It is found that scintillation
occurrence is essentially a night-time phenomenon and day-time scintillations are very rare. Annual average nocturnal variation
of percentage occurrence of scintillations shows maximum at around 2100–2200 hours LT. Seasonally, scintillations are most
prominent during equinoxes and least during summer. Geomagnetic disturbances tend to decrease the occurrence of scintillations
in the pre-midnight period. 相似文献
9.
处于高纬向日面的极隙区是太阳风能量、动量和质量可以直接进入地球磁场并到达地球的近地空间的区域。本文简要介绍了极隙区的观测和研究,综述了极隙区的粒子沉降、场向电流、等离子体对流和电离层电流的特征。 相似文献
10.
1998年5月磁暴磁层电流体系的地磁效应分析 总被引:3,自引:3,他引:3
低纬度地区地磁场的短时变化主要由以下电流体系产生:电离层发电机电流(IDC)、对称环电流(SRC)以及由部分环电流和Ⅱ区场向电流及其电离层回路组成的内磁层三维电流体系(PRFI).此外,由Ⅰ区场向电流及其电离层回路组成的电流体系(FACI)所产生的低纬地磁场也是不可忽略的.本文针对1998年5月1-6日的大磁暴,首先利用多个同子午线台站对的数据分离并消去由IDC电流产生的Sq场.然后,通过线性建模分离其他电流体系产生的磁场成分.结果表明:(1)发生在5月1-6日的磁暴可以分为两个过程,PRFI和FACI电流体系在1-3日不明显,在4-5日伴随着亚暴强烈发生.(2)SRC的变化情况在第一阶段同Dst指数相似,在第二阶段明显滞后于Dst指数.(3)在5月4-5日,PRFI在SRC之前增强,随着PRFI和FACI的恢复,SRC开始增强.这一结果为我们了解环电流和场向电流的形成以及它们的关系提供线索. 相似文献