Propagation Direction Analyses of Medium‐Scale Traveling Ionospheric Disturbances Observed Over North America With GPS‐TEC Perturbation Maps by Three‐Dimensional Spectral Analysis Method
Propagation Direction Analyses of Medium‐Scale Traveling Ionospheric Disturbances Observed Over North America With GPS‐TEC Perturbation Maps by Three‐Dimensional Spectral Analysis Method
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DOI：
10.1029/2020ja028791
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发表时间：
2022-01
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通讯作者：
S. Perwitasari;Takuji Nakamura;T. Tsugawa;M. Nishioka;Y. Tomikawa;M. Ejiri;Masaru Kogure;Y. Otsuka;A. Shinbori;H. Jin;Chengcheng Tao
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作者：
S. Perwitasari;Takuji Nakamura;T. Tsugawa;M. Nishioka;Y. Tomikawa;M. Ejiri;Masaru Kogure;Y. Otsuka;A. Shinbori;H. Jin;Chengcheng Tao
我们将一种新的三维谱分析方法应用于GPS‐TEC扰动（GPS‐TECP）图，以研究北美白天和夜间中等尺度电离层扰动（MSTID）的传播方向。利用该方法可以自动计算MSTID的相速度谱和方向性。我们集中在MSTID的高发生期，即2006年6月至7月和2006年11月至12月，研究夜间和白天的MSTID。我们把北美洲分为西部（100°-130 ° W，25°-55 ° N）和东部（70°-100 ° W，25°-55 ° N）两部分。我们的研究结果表明，白天和夜间MSTID传播表现出强烈的纵向变化作为当地时间和日常变化的函数。白天MSTID的功率峰值在西部的10：00-16：00 LT和东部的10：00-14：00 LT。白天MSTID的主要传播方向是西（东）向南（东南）。白天当地时间的变化表明，在西部的MSTID显示方向的变化，但是，类似的方向变化是不是很明显，在东部。夜间MSTID的本地时间变化表现为西部22：00-02：00 LT和东部20：00-00：00 LT的功率峰值。结果表明，西半球的主要传播方向是向西的，其方位带（φ 210° ~ 300 °）比东半球（φ 210° ~ 240 °）宽。通过对东西半球夜间电波传播方向的比较，得出了磁偏角影响电波传播方向的结论。
We applied a novel three‐dimensional spectral analysis method to GPS‐TEC perturbation (GPS‐TECP) maps to study the propagation direction of daytime and nighttime medium‐scale traveling ionospheric disturbances (MSTIDs) over North America. By this method, we can automatically calculate the phase velocity spectrum and directionality of MSTIDs. We focused on the periods of high MSTIDs occurrence, namely, June–July 2006 and November–December 2006, to study nighttime and daytime MSTIDs. We divided North America into the west (100°–130°W, 25°–55°N) and east (70°–100°W, 25°–55°N) parts. Our results show that both daytime and nighttime MSTID propagations exhibit strong longitudinal variations as a function of local time and day‐to‐day variations. The power peaks of daytime MSTIDs are from 10:00–16:00 LT in the west part and 10:00–14:00 LT in the east part. The predominant propagation directions of daytime MSTIDs are southward (southeastward) in the west (east). The daytime local time variations demonstrate that the MSTIDs display directional change in the west part; however, a similar directional change is not very pronounced in the east part. The local time variations of nighttime MSTIDs shows the power peaks from 22:00–02:00 LT in the west and 20:00–00:00 LT in the east. We found that the predominant propagation direction in the west part is westward with a wider azimuthal band (∼210°–300°) than the east part (∼210°–240°). By comparing nighttime propagation directions between the western and eastern parts, we reached the conclusion that the magnetic declination angle affects the propagation direction.