Department of Physical Sciences, Embry-Riddle Aeronautical University, Daytona Beach, FL 32114, USA.
Illinois Institute of Technology, Chicago, IL 60616, USA.
Sensors (Basel). 2023 Feb 23;23(5):2477. doi: 10.3390/s23052477.
Electron density irregularities in the ionosphere modify the phase and amplitude of trans-ionospheric radio signals. We aim to characterize the spectral and morphological features of E- and F-region ionospheric irregularities likely to produce these fluctuations or "scintillations". To characterize them, we use a three-dimensional radio wave propagation model-"Satellite-beacon Ionospheric scintillation Global Model of upper Atmosphere" (SIGMA), along with the scintillation measurements observed by a cluster of six Global Positioning System (GPS) receivers called Scintillation Auroral GPS Array (SAGA) at Poker Flat, AK. An inverse method is used to derive the parameters that describe the irregularities by estimating the best fit of model outputs to GPS observations. We analyze in detail one E-region and two F-region events during geomagnetically active times and determine the E- and F-region irregularity characteristics using two different spectral models as input to SIGMA. Our results from the spectral analysis show that the E-region irregularities are more elongated along the magnetic field lines with rod-shaped structures, while the F-region irregularities have wing-like structures with irregularities extending both along and across the magnetic field lines. We also found that the spectral index of the E-region event is less than the spectral index of the F-region events. Additionally, the spectral slope on the ground at higher frequencies is less than the spectral slope at irregularity height. This study describes distinctive morphological and spectral features of irregularities at E- and F-regions for a handful of cases performed using a full 3D propagation model coupled with GPS observations and inversion.
电离层中的电子密度不规则会改变跨电离层无线电信号的相位和幅度。我们旨在描述可能产生这些波动或“闪烁”的 E 层和 F 层电离层不规则的谱和形态特征。为了对其进行描述，我们使用了一个三维无线电波传播模型——“卫星信标电离层闪烁全球上层大气模型”（SIGMA），并结合了在阿拉斯加 Poker Flat 的 Scintillation Auroral GPS Array（SAGA）六个全球定位系统（GPS）接收器观察到的闪烁测量结果。通过使用反演方法，我们通过估计模型输出与 GPS 观测的最佳拟合来推导出描述不规则性的参数。我们详细分析了地磁活动期间的一个 E 层和两个 F 层事件，并使用 SIGMA 的两个不同谱模型作为输入来确定 E 层和 F 层不规则性的特征。我们从谱分析中得到的结果表明，E 层不规则性更沿着磁力线拉长，呈杆状结构，而 F 层不规则性具有翼状结构，不规则性沿着和横跨磁力线延伸。我们还发现，E 层事件的谱指数小于 F 层事件的谱指数。此外，地面上较高频率处的谱斜率小于不规则性高度处的谱斜率。本研究使用全 3D 传播模型结合 GPS 观测和反演，对少数情况下 E 层和 F 层不规则性的独特形态和谱特征进行了描述。
