The ionosphere over the Brazilian region has particular characteristics due to the large geomagnetic declination angle over most of the territory. Furthermore, the equatorial ionization anomaly southern crest is located over the Brazilian territory. In this region, plasma irregularities may arise in the post-sunset hours. These ionospheric irregularities develop in the form of magnetic field-aligned plasma depletions, known as equatorial plasma bubbles, which may seriously affect radio signals that propagate through them. These irregularity structures can cause amplitude and phase scintillation of the propagating signals, thereby compromising the availability, performance, and integrity of satellite-based communication and navigation systems. Additionally, the total electron content (TEC) introduces propagation delays that can contribute to range measurement errors for global positioning system (GPS) users. The ionospheric characteristics change significantly according to the time of day, season, as well as the solar and geomagnetic activities, among other factors. Indeed, the ionosphere is one of the most significant sources of errors in the positioning and navigation systems based on the GPS satellites. Due to these features, there is a strong interest by the scientific community in better understanding and characterizing the ionospheric behavior. In this context, the TEC analysis has wide applicability for space plasma studies and is a well-established tool for investigating the ionospheric behavior and its potential impact on space-based navigation systems. One of the goals of these studies is the generation of TEC maps for a geographic region based on GPS observations. In the present work, some electrodynamic processes of the low-latitude ionosphere are reviewed and the TEC estimation based on GPS measurements is revisited in detail. A methodology aimed at creating the TEC maps is presented and validated by comparison with results from other geophysical instruments, such as all-sky imagers and ionosondes. Finally, examples of the ionospheric behavior displayed by TEC maps during equatorial plasma bubble events and a geomagnetic storm are fully described and discussed.

中文翻译：

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低纬度电离层总电子含量图中等离子体气泡特征的分析：一种简化的方法

由于巴西地区大部分地区的地磁偏角很大，因此巴西地区的电离层具有特殊的特征。此外，赤道电离异常南峰位于巴西领土上空。在该地区，日落后可能会出现血浆不规则性。这些电离层的不规则性以磁场对齐的等离子体损耗的形式发展，称为赤道等离子体气泡，这可能会严重影响通过它们传播的无线电信号。这些不规则结构会导致传播信号的幅度和相位闪烁，从而危及基于卫星的通信和导航系统的可用性、性能和完整性。此外，总电子含量 (TEC) 会引入传播延迟，这可能会导致全球定位系统 (GPS) 用户的距离测量误差。电离层特性根据一天中的时间、季节以及太阳和地磁活动等因素发生显着变化。事实上，电离层是基于 GPS 卫星的定位和导航系统中最重要的误差来源之一。由于这些特征，科学界对更好地理解和表征电离层行为有着浓厚的兴趣。在此背景下，TEC 分析对空间等离子体研究具有广泛的适用性，并且是研究电离层行为及其对天基导航系统的潜在影响的完善工具。这些研究的目标之一是基于 GPS 观测生成地理区域的 TEC 地图。在目前的工作中，回顾了低纬度电离层的一些电动力过程，并详细重新审视了基于 GPS 测量的 TEC 估计。通过与其他地球物理仪器（如全天成像仪和电离探空仪）的结果进行比较，提出并验证了一种旨在创建 TEC 地图的方法。最后，充分描述和讨论了赤道等离子体气泡事件和地磁风暴期间 TEC 地图显示的电离层行为示例。回顾了低纬度电离层的一些电动力学过程，并详细重新审视了基于 GPS 测量的 TEC 估计。通过与其他地球物理仪器（如全天成像仪和电离探空仪）的结果进行比较，提出并验证了一种旨在创建 TEC 地图的方法。最后，充分描述和讨论了赤道等离子体气泡事件和地磁风暴期间 TEC 地图显示的电离层行为示例。回顾了低纬度电离层的一些电动力学过程，并详细重新审视了基于 GPS 测量的 TEC 估计。通过与其他地球物理仪器（如全天成像仪和电离探空仪）的结果进行比较，提出并验证了一种旨在创建 TEC 地图的方法。最后，充分描述和讨论了赤道等离子体气泡事件和地磁风暴期间 TEC 地图显示的电离层行为示例。