Evolution of Mid‐latitude Density Irregularities and Scintillation in North America During the 7–8 September 2017 Storm
Evolution of Mid‐latitude Density Irregularities and Scintillation in North America During the 7–8 September 2017 Storm
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DOI：
10.1029/2021ja029192
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发表时间：
2021-06
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通讯作者：
Y. Nishimura;S. Mrak;J. Semeter;A. Coster;P. Jayachandran;K. Groves;D. Knudsen;N. Nishitani;J. Ruohoniemi
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作者：
Y. Nishimura;S. Mrak;J. Semeter;A. Coster;P. Jayachandran;K. Groves;D. Knudsen;N. Nishitani;J. Ruohoniemi
利用北美大学导航星联盟 (UNAVCO) 全球定位系统 (GPS) 接收器网络，我们展示了 2017 年 9 月 7 日至 8 日风暴期间中纬度电离层中 GPS 无线电信号闪烁的二维分布。中纬度电离层在风暴主要阶段和早期恢复阶段表现出多种密度结构，如风暴增强密度（SED）基底和羽流、主槽、次级羽流和次级槽。在这些结构的密度梯度处观察到增强的相位和振幅闪烁指数。 SuperDARN 雷达回波在密度梯度处也得到增强。闪烁和高频雷达回波的搭配表明，中纬度密度结构在很宽的波长范围（数十米到数十公里）内出现了密度不规则性。 Swarm 和 DMSP 还检测到密度梯度和不规则性作为干扰 GPS 信号的原位密度结构。不规则性占背景密度的很大一部分（~10%–50%）。密度不规则性的幂律谱的斜率约为−1.8，表明梯度漂移不稳定性（GDI）有助于湍流的形成。高纬度和低纬度过程都可能有助于形成中纬度密度结构，并且中纬度闪烁发生在高纬度和低纬度强迫的交界处。
Using the University Navstar Consortium (UNAVCO) Global Positioning System (GPS) receiver network in North America, we present 2‐D distributions of GPS radio signal scintillation in the mid‐latitude ionosphere during the 7–8 September 2017 storm. The mid‐latitude ionosphere showed a variety of density structures such as the storm enhanced density (SED) base and plume, main trough, secondary plume, and secondary trough during the storm main and early recovery phases. Enhanced phase and amplitude scintillation indices were observed at the density gradients of those structures. SuperDARN radar echoes were also enhanced at the density gradients. The collocation of the scintillation and HF radar echoes indicates that density irregularities developed across a wide range of wavelengths (tens of meters to tens of kilometers) in the mid‐latitude density structures. The density gradients and irregularities were also detected by Swarm and DMSP as in‐situ density structures that disturbed the GPS signals. The irregularities were a substantial fraction (∼10%–50%) of the background density. The density irregularity had a power law spectrum with slope of ∼ −1.8, suggesting that gradient drift instability (GDI) contributed to turbulence formation. Both high‐latitude and low‐latitude processes likely contributed to forming the mid‐latitude density structures, and the mid‐latitude scintillation occurred at the interface of high‐latitude and low‐latitude forcing.