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排序方式: 共有134条查询结果,搜索用时 15 毫秒
1.
A theoretical model for mid-and low-latitude ionospheric electric fields in realistic geomagnetic fields 总被引:1,自引:1,他引:0
The geomagnetic fields, which play important roles in the ionospheric dynamo, can greatly affect the global distribution of ionospheric electric fields, currents and other ionospheric electrodynamics phenomena. In the study of ionospheric electrodynamics phenomena, such as the longitudinal variations of ionospheric electric fields, the non-dipolar component of the geomagnetic fields must be taken into account. In this paper, we deduce a theoretical electric field model for ionospheric dynamo at mid- and low-latitude which adopt a modified magnetic apex coordinates system. In the new electric field model, the geomagnetic fields can be calculated from either the IGRF model or the dipole field model, and the neutral winds and conductivities are calculated based on empirical models. Then the dynamo equation for the electric potential is finally solved in terms of the line-by-line iteration method, and the ionospheric electric fields and currents are derived from the calculated potential. Our model can reproduce the main features of the ionospheric electrodynamics processes, so it will be a useful tool for the investigation of the upper atmosphere and ionosphere. 相似文献
2.
3.
Ionospheric eclipse factor method (IEFM) for determining the ionospheric delay using GPS data 总被引:1,自引:0,他引:1
By establishing the ionospheric eclipse factor (IEF) λ of the ionospheric pierce point (IPP) and its ionospheric influence factor (IFF) λ, and combining λ, λ with t of IPP, a new method of modeling high-precision ionospheric delay using GPS data-ionospheric eclipse factor method (IEFM)-is presented in this paper. The IEFM can effectively select the proper ionospheric models to model the total electron content (TEC) with different changes corresponding to annual, seasonal and diurnal variations. Initial experimental results show that the correction precision of ionospheric delay modeled by the IEFM seems to be close to that of using L3 GPS observations to directly correct the corresponding ionospheric delay. 相似文献
4.
Yong Wei QiuGang Zong ZuYin Pu WeiXing Wan JianJun Liu SuiYan Fu QuanQi Shi 《科学通报(英文版)》2011,56(11):1117-1122
It is believed that a southward interplanetary magnetic field (IMF) is mainly responsible for the energy input from solar
wind into the magnetosphere. This paper presents an unusual case of strong anti-sunward plasma flow (up to 2 km/s) in the
polar cap ionosphere and large cross-polar cap potential (CPCP) during a period of horizontal IMF (|B
Z
| < 2 nT) observed by both ACE (at the L1 point) and Geotail (on the dusk flank of the magnetosheath). The CPCP is even higher
than that under preceding B
Z
≈ −23 nT. Furthermore, GOES8 observed that the magnetosheath field turns northward as the anti-sunward plasma flow and CPCP
start to increase, which implies that the magnetosheath field interacting with the Earth’s magnetopause has significantly
rotated and differs from the IMF observed by ACE and Geotail. In accordance with previous theoretical work, we suggest that
the magnetic field line draping produces a southward magnetosheath field and enhances anti-sunward plasma flow and the CPCP. 相似文献
5.
太阳高年期间海南电离层扩展F出现的起始时间研究 总被引:1,自引:0,他引:1
电离层扩展F与电离层闪烁现象密切相关,它们出现的起始时间存在着很大程度上的一致性,因此研究电离层扩展F出现的起始时间将对闪烁预报模型的建立具有重要的应用价值.将太阳高年(2002年3月-2003年2月)期间海南地区DPS-4测高仪观测到的扩展F按照频率、区域、混合和强区域扩展等分为四种类型,对其出现的起始时间进行了分析研究.结果表明:频率扩展和混合扩展的起始时间分别集中在0200LT-0800LT和0000LT-0600LT;而区域扩展和强区域扩展出现的起始时间分别集中在2000LT-0200LT和2000LT-2200LT. 相似文献
6.
On the basis of the analysis of the system sounding principle, this paper introduced a new type of ionospheric oblique backscattering
sound system, which is based on the pseudo- random noise phase modulated pulse compression. According to the high requirements
of real-time and a large amount of computation and echo characteristics, a high-speed real-time signal processing system was
established and the design of system hardware and software was focused on. The sounding results indicate that the system is
equipped to handle the data fast and has a high degree of software features. It is of great significance for the realization
of fast, real-time ionospheric sounding means.
相似文献
7.
L.?Marié J.?Burguete F.?DaviaudEmail author J.?Léorat 《The European Physical Journal B - Condensed Matter and Complex Systems》2003,33(4):469-485
A numerical study of the magnetic induction equation has
been performed on von Kármán type flows. These flows are
generated by two co-axial counter-rotating propellers in
cylindrical containers. Such devices are currently used in the
von Kármán sodium (VKS) experiment designed to study dynamo
action in an unconstrained flow. The mean velocity fields have
been measured for different configurations and are introduced in
a periodic cylindrical kinematic dynamo code. Depending on the
driving configuration, on the poloidal to toroidal flow ratio
and on the conductivity of boundaries, some flows are observed
to sustain growing magnetic fields for magnetic Reynolds numbers
accessible to a sodium experiment. The response of the flow to
an external magnetic field has also been studied: The results
are in excellent agreement with experimental results in the
single propeller case but can differ in the two propellers case. 相似文献
8.
C B Dwivedi 《Pramana》2000,55(5-6):849-854
Theoretical prediction of a new kind of normal mode behaviour of electro-mechanical nature was first time reported by Dwivedi
and Das in 1992 in the context of mesospheric modeling of observed neutral induced turbulence. Local dynamo action (due to
relative neutral flow) governs the basic physical principle for linear excitation of the neutral induced low frequency instability
(NILF) in mesospheric plasma, which comprises of weakly ionized inhomogeneous gas confined by the external gravity and ambient
magnetic field. The present contribution offers physical explanation in terms of dynamo transformation of neutral drag effect
as a source to understand complete suppression of the usual collisional R-T and in turn linear driving of the NILF. It is
therefore emphasized, worth calling it as the dynamo instability. 相似文献
9.
吴玮 《南京工业大学学报(自然科学版)》2015,37(1)
给出了利用双频观测值计算L3组合电离层延迟高阶项改正的方法,并与全球电离层延迟文件的改正效果进行对比.利用赤道附近的15个国际全球卫星导航定位系统服务组织(IGS)站的数据进行比较,结果表明:2种方法计算的电离层二阶项延迟互差最大不超过1 cm,三阶项延迟互差最大不超过5 mm;电离层高阶项改正后的观测值精密单点定位(PPP)解算结果N、E、U方向互差平均值分别为0.4、0.5、1.0mm,因此2种改正方法效果在同一水平. 相似文献
10.
设计并开发了一种人工扰动电离层仿真系统.建立了数值模型,规划出系统总体构造,在实现过程中引入VC、VF混合编程的概念,以达到两种语言优势互补的目的.文中详细论述了VC、VF混合编程对于数据的处理,生成Fortran的动态链接库,以及在VC中调用生成库的技术.通过仿真模拟,得出了电离层加热过程中电子密度、电子温度等随时间演化的规律,及发射电波频率、功率对加热效果的影响.试用证明,该系统有效地模拟了电离层人工扰动的状态,为在我国实施加热工程提供了可靠的科学依据. 相似文献