Ray tracing technique for global 3‐D modeling of ionospheric electron density using GNSS measurements
Ray tracing technique for global 3‐D modeling of ionospheric electron density using GNSS measurements
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DOI：
10.1002/2014rs005466
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发表时间：
2015-06
期刊：
影响因子：
1.6
通讯作者：
M. M. Alizadeh-M.;H. Schuh;M. Schmidt
中科院分区：
文献类型：
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作者：
M. M. Alizadeh-M.;H. Schuh;M. Schmidt
空间大地测量技术工作在微波波段，电离层是色散介质；因此，在这种介质中传播的信号处于第一近似状态，受影响的频率与它们的平方成反比。这种效应使我们能够获得有关电离层总电子含量（TEC）或电子密度（Ne）等参数的信息。利用这一现象，空间大地测量技术在过去几十年中已经成为研究电离层的有力工具。目前，垂直TEC （Vertical TEC， VTEC）的二维模型已经得到了广泛的开发和应用；然而，由于这些模型提供了沿垂直或倾斜射线路径的整个电子含量的积分信息，当需要关于不同高度电离层的信息时，这些图就没有用了。本文介绍了最近的一项研究，该研究旨在利用全球导航卫星系统的测量结果，并将射线追踪技术应用于高层大气，建立一个全球电子密度的三维模型。所开发的建模方法表示电子密度的水平变化，具有两组15次和15阶的球谐展开。电子密度的高度依赖性由电离层底部和顶部的多层查普曼剖面函数和等离子层的适当模型来表示。除了已开发模型的大地测量应用之外，在本研究中，电子密度的三维模型可以包括地球物理参数，如最大电子密度及其相应的高度。这些参数的高分辨率建模可以改进地球物理解释，这在高层大气、空间天气和日地环境的所有研究中都是必不可少的。
For space geodetic techniques, operating in microwave band, ionosphere is a dispersive medium; thus, signals traveling through this medium are in the first approximation, affected proportional to the inverse of the square of their frequencies. This effect allows gaining information about the parameters of the ionosphere in terms of total electron content (TEC) or the electron density (Ne). Making use of this phenomenon, space geodetic techniques have turned into a capable tool for studying the ionosphere in the last decades. Up to now, two‐dimensional (2‐D) models of Vertical TEC (VTEC) have been widely developed and used by different communities; however, due to the fact that these models provide information about the integral of the whole electron content along the vertical or slant raypath, these maps are not useful when information about the ionosphere at different altitude is required. This paper presents a recent study which aims at developing a global 3‐D model of the electron density, using measurements from Global Navigation Satellite Systems and by applying the ray tracing technique to the upper atmosphere. The developed modeling approach represents the horizontal variations of the electron density, with two sets of spherical harmonic expansions of degree and order 15. The height dependency of the electron density is represented by a multilayered Chapman profile function for the bottomside and topside ionosphere, and an appropriate model for the plasmasphere. In addition to the geodetic applications of the developed models, within this study, the 3‐D models of electron density can include geophysical parameters like maximum electron density and its corresponding height. High‐resolution modeling of these parameters allows an improved geophysical interpretation, which is essential in all studies of the upper atmosphere, space weather, and for the solar‐terrestrial environment.