Determination of the Refractive Contribution to GPS Phase “Scintillation”
Determination of the Refractive Contribution to GPS Phase “Scintillation”
复制标题
DOI：
10.1029/2018ja025759
复制
发表时间：
2019-02
期刊：
影响因子：
--
通讯作者：
A. McCaffrey;P. Jayachandran
中科院分区：
文献类型：
--
作者：
A. McCaffrey;P. Jayachandran
当L波段的无线电波穿过电离层时，如由全球定位系统卫星发射的无线电波，沿射线路径的电子密度的变化可能会引起信号相位的折射和/或衍射变化；其中折射变化是确定性的，而衍射变化是随机的。通常，这些变化的折射分量被认为是缓慢变化的，与低于0.1赫兹的频率有关。因此，如果假设折射贡献与小于0.1赫兹的频率相关联，则假设大于0.1赫兹的频率并将其视为衍射波。这些变化通常被称为闪烁。在闪烁研究中，确定性的折射变化常常被忽略。我们认为，电子密度的快速变化，从而导致沿GPS信号射线路径的折射率的变化，可以在大于0.1赫兹的频率上引起主要的折射率变化。在高纬度地区观测到的漂移速度的增加为这些高频折射变化创造了适宜的条件；GPS射线路径将以更高的速度扫过大范围的不规则性，导致高频折射变化。利用GPS的最新进展，最重要的是一种改进的信号跟踪技术，我们提供了GPS信号相位快速折射变化的例子。这些高频变化被证明是折射的，使用了多种技术的组合，一种是从以前用于低频折射贡献的技术改编而来的，另一种是只有在GPS跟踪方面的进步才可能实现的新技术。
As L‐band radio waves travel through the ionosphere, such as those transmitted by the Global Positioning System (GPS) satellites, changes in the electron density along the ray path may induce refractive and/or diffractive variations in the signal's phase; where refractive variations are deterministic and diffractive variations are stochastic. Typically, the refractive component of these variations is thought to be slow varying, associated with frequencies less than 0.1 Hz. Therefore, if the refractive contribution is assumed to be associated with frequencies less than 0.1 Hz, the frequencies greater than 0.1 Hz are then assumed and treated as diffractive. These variations are usually referred to as scintillation. In scintillation studies the deterministic refractive variations are very often ignored. We propose that rapid changes in the electron density, and therefore changes in the refractive index along the ray path of the GPS signal, can induce dominantly refractive variations at frequencies greater than 0.1 Hz. The increased drift speeds observed in the high‐latitude region create conditions suitable for these high‐frequency refractive variations; the GPS ray path will sweep through large‐scale irregularities at higher speeds, resulting in high‐frequency refractive variations. Using recent advances in GPS, most importantly an improved signal tracking technique, we present examples of rapid refractive variations in the GPS signal's phase. These high‐frequency variations are shown to be refractive using a combination of techniques, one adapted from a previous technique used for the low‐frequency refractive contributions and a new technique only possible with advances in GPS tracking.