Institute of Earth Sciences, Academia Sinica, Taipei 11529, Taiwan.
North Information Control Research Academy Group Co., Ltd., Nanjing 211153, China.
Sensors (Basel). 2020 Jan 19;20(2):540. doi: 10.3390/s20020540.
It is of great significance for the global navigation satellite system (GNSS) service to detect the polar ionospheric total electron content (TEC) and its variations, particularly under disturbed ionosphere conditions, including different phases of solar activity, the polar day and night alternation, the Weddell Sea anomaly (WSA) as well as geomagnetic storms. In this paper, four different models are utilized to map the ionospheric TEC over the Arctic and Antarctic for about one solar cycle: the polynomial (POLY) model, the generalized trigonometric series function (GTSF) model, the spherical harmonic (SH) model, and the spherical cap harmonic (SCH) model. Compared to other models, the SCH model has the best performance with ±0.8 TECU of residual mean value and 1.5-3.5 TECU of root mean square error. The spatiotemporal distributions and variations of the polar ionospheric TEC are investigated and compared under different ionosphere conditions in the Arctic and Antarctic. The results show that the solar activity significantly affects the TEC variations. During polar days, the ionospheric TEC is more active than it is during polar nights. In polar days over the Antarctic, the maximum value of TEC always appears at night in the Antarctic Peninsula and Weddell Sea area affected by the WSA. In the same year, the ionospheric TEC of the Antarctic has a larger amplitude of annual variation than that of the TEC in the Arctic. In addition, the evolution of the ionization patch during a geomagnetic storm over the Antarctic can be clearly tracked employing the SCH model, which appears to be adequate for mapping the polar TEC, and provides a sound basis for further automatic identification of ionization patches.
对于全球导航卫星系统（GNSS）服务来说，检测极区电离层总电子含量（TEC）及其变化具有重要意义，尤其是在受扰电离层条件下，包括不同太阳活动阶段、极昼和极夜交替、威德尔海异常（WSA）以及地磁暴等情况。本文利用四种不同的模型来绘制北极和南极的电离层 TEC，时间跨度约为一个太阳活动周期：多项式（POLY）模型、广义三角函数级数函数（GTSF）模型、球谐（SH）模型和球冠谐（SCH）模型。与其他模型相比，SCH 模型的表现最好，其残差均值为±0.8 TECU，均方根误差为 1.5-3.5 TECU。在北极和南极，根据不同的电离层条件，研究和比较了极区电离层 TEC 的时空分布和变化情况。结果表明，太阳活动对 TEC 变化有显著影响。极昼期间，电离层 TEC 比极夜期间更为活跃。在南极极昼期间，南极半岛和威德尔海受 WSA 影响的地区，TEC 的最大值总是出现在夜间。同年，南极电离层 TEC 的年变化幅度比北极 TEC 的年变化幅度大。此外，利用 SCH 模型可以清晰地跟踪南极地区地磁暴期间电离斑的演化，该模型对于绘制极区 TEC 是足够的，并为进一步自动识别电离斑提供了良好的基础。
